**Scientific Objectives of the Fifth [C]{.underline}onvection
[A]{.underline}nd [M]{.underline}oisture [Ex]{.underline}periment
(CAMEX-5)**

** **

**Proposed by the CAMEX-4 Science Team**

** **

**30 October 2003**

# EXECUTIVE SUMMARY {#executive-summary .unnumbered}

The mission of the NASA Earth Science Enterprise (ESE) is to develop a
scientific understanding of the Earth system and its responses to
natural and human-induced changes in order to improve the prediction of
climate, weather, and natural hazards. In this role, the NASA ESE
develops scientific research and measurement strategies investigating
the land, ocean, and atmospheric components of the Earth system and
their interactions. These investigations, which cover a broad continuum
of spatial and temporal scales, focus on general research themes of
climate variability and change, the water and energy cycle, weather,
atmospheric composition, the Earth surface and interior, and carbon
cycle, ecosystem and biogeochemistry processes. These themes encompass
23 basic questions outlined by Asrar et al. (2001) as NASA ESE research
priorities needed to improve the understanding of global Earth system
variability, primary forces, response mechanisms, consequences of
change, and predictability of future change.

One of the NASA ESE investigations contributing to the climate, water,
and weather research themes is the Convection And Moisture Experiment
(CAMEX), which responds to the following subset of the 23 NASA ESE
research questions. Namely,

-   How are the global precipitation, evaporation, and the cycling of
    water changing?

-   How are the variations in local weather, precipitation, and water
    resources related to global climate variation?

-   How can weather forecast duration and reliability be improved by new
    space-based observations, data assimilation, and modeling?

CAMEX, which was primarily designed to validate satellite measurements
of moisture and to create a better understanding of the water cycle,
also places an emphasis upon studies of tropical cyclones (TC).
Utilizing NASA expertise in remote sensing and spaceborne observations,
the CAMEX tropical cyclone goals are to increase the overall
understanding of TC behavior, identify remote sensing measurements and
modeling requirements for improved hurricane predictability, and to
validate the performance of NASA spaceborne sensors to accurately
monitor the short-term impacts and long-term trends of tropical storms
and hurricanes. These goals have lead to a strong collaborative
partnership with the Hurricane Research Division (HRD) of the National
Oceanic and Atmospheric Administration (NOAA) Atlantic Oceanographic and
Meteorological Laboratory and the United States Weather Research Program
(USWRP) who have similar goals to advance the understanding and
predictability of hurricanes as part of their responsibility to expedite
the transfer of hurricane research advancements to operational
forecasting enhancements.

The centerpiece of the CAMEX effort has been a series of field research
campaigns employing spaceborne, airborne, and ground-based assets with a
particular emphasis on remote sensing observations. Four field campaigns
have been conducted during an eight-year period between 1993-2001. The
first two provided a performance test bed for new airborne or
ground-based instrumentation designed to simulate or complement
precipitation and moisture observations made by satellite sensors. The
latter two field campaigns incorporated many of the early CAMEX sensors
into a larger, more complete collection of remote sensing and *in situ*
devices for a focused investigation of tropical storms, hurricanes, and
convection. These latter two experiments, which were called CAMEX-3 and
CAMEX-4, were based in Florida during 1998 and 2001, respectively, in
order to sample tropical cyclones in the western Atlantic Ocean basin
and the Gulf of Mexico while also supporting validation activities for
the Tropical Rainfall Measuring Mission (TRMM). Joint aircraft missions
with NOAA HRD during CAMEX-3 and CAMEX-4 successfully sampled a total of
eight tropical storms and hurricanes. Many of the findings from these
field campaigns have been published or are being prepared for
publication in a special issue of the American Meteorological Society
*Journal of Atmospheric Sciences.* These results highlight
interpretations of CAMEX observations of TC convection, wind, moisture,
microphysics, and temperature for improved model representations of TC
intensity change, motion, rainfall potential, and landfalling impacts.

The success of the CAMEX research and the strong partnership forged
between NASA, NOAA, and USWRP represents a sturdy rung of the ladder
being built by many of the scientific community to reach a greater
understanding and improved predictability of tropical cyclone behavior.
Yet, many more rungs in the ladder still remain to be built. Improved
skill in prediction of TC genesis, intensity change, and rainfall
potential are just a few of these rungs requiring attention due to
deficiencies in the understanding of the physical processes involved and
additional deficiencies in numerical model parameterizations and data
assimilation inputs. The spaceborne and suborbital observational
capabilities and technological development activities of NASA put it in
a unique position to assist the hurricane research community in
addressing these deficiencies, while also tackling the NASA ESE mission
goal to understand and predict changes to the total Earth system. In
particular, the launch of several new satellites, such as Aqua, Jason-1,
and CloudSat, during the 2001-2005 time frame and the prospect of using
uninhabited aerial vehicles (UAV) for hurricane monitoring during the
next decade offer new research tools that need to explored and
validated. Thus, the timing is right to consider a new field phase of
CAMEX to support the validation and utilization of new satellite
products while also demonstrating the impact that higher spatial and
temporal resolution airborne information from UAV platforms might
contribute to forecast improvements.

The timing is also right to assess the gaps in knowledge that still
exist for CAMEX. Operational requirements and NASA goals for five-day
forecasts and beyond necessitate an accurate knowledge of the
contributing factors to hurricane genesis and intensity change. However,
previous CAMEX field operations have not adequately obtained
observations related to tropical cyclone genesis due to the rare
instances of these types of systems at the previous deployment
locations. Airborne measurements of cloud and precipitation properties
have led to improved microphysical parameterizations, but have also
pointed out the need for measurements at a greater variety of
atmospheric temperature levels. Numerical modeling efforts have
demonstrated a requirement for higher resolution humidity information to
drive the model convection, but additional observations in the tropical
cyclone core and synoptic environment are needed to initialize and
validate these models. New partnerships with other NASA ESE research
teams are also recommended to ensure a more complete understanding of
tropical cyclone behavior and water cycle variability within the context
of the total Earth system.

In order to contribute to the NASA ESE mission and build upon the
strengths of NASA expertise to assist the hurricane research community,
the CAMEX-4 Science Team recommends that a new field experiment, called
CAMEX-5, be conducted to address the understanding and prediction of
tropical genesis, intensity, motion, rainfall potential, and landfall
impacts by remote and *in situ* sensing of the three phases of water
from spaceborne and airborne platforms. Hurricane behavior is a
multi-scale problem: the hurricane vortex is hundreds of km in
horizontal scale, but the eye and eyewall are tens of km (mesoscale),
and the embedded convective clouds are order of km (cloud scale). In
addition, hurricanes are heavily influenced by phenomena in their
environment that are thousands of km wide (synoptic scale). In CAMEX-5,
it is proposed to address the broader goals of CAMEX by specifically
considering each scale of motion and how it interacts with other scales.
A specific set of questions has been generated for each scale of
interest. For the synoptic scale, these questions are as follows:

1.  What are the roles of environmental vertical wind shear in tropical
    cyclone genesis, intensification, track, and rainfall?

2.  **How does the amount and distribution of environmental moisture
    contribute to tropical cyclone genesis, intensification, track, and
    rainfall?**

3.  **How do large-scale effects, such as interactions between easterly
    waves, terrain, upper-level troughs, atmospheric dust layers, and
    the Intertropical Convergence Zone, contribute to tropical
    cyclogenesis and intensity change?**

4.  **What are the capabilities and limitations of using spaceborne and
    airborne information to improve forecasts of tropical cyclone track,
    intensity, and rainfall?**

> For mesoscale processes, they are:

5.  How does a surface circulation develop?

6.  What controls the timing, location, and intensity of convection and
    precipitation and how do these processes feedback to the vortex?

7.  Do radiative processes and cloud-radiation interactions contribute
    to storm development and intensification?

8.  How are developing and mature systems impacted by landfall?

> For cloud scale processes, they are:

9.  How can the representations of hurricane microphysics be improved
    through the use of *in situ* and remotely sensed microphysical
    quantities?

10. How can quantitative precipitation forecasts be improved through
    application or assimilation of remotely sensed microphysical
    quantities as well as better representations of microphysical,
    boundary layer, thermodynamic, and other processes?

11. How does the release of latent heat from microphysical processes
    feedback upon the updraft and downdraft characteristics of
    hurricanes and their evolution?

The recommended CAMEX-5 deployment location for the NASA aircraft is
Costa Rica. This site will be conducive to addressing all of the science
questions raised earlier while significantly improving the opportunities
for sampling tropical cyclogenesis scenarios. The eastern tropical
Pacific Ocean, on average, experiences more tropical cyclones each
season than the Atlantic Ocean.  In contrast to the Atlantic, which can
have TCs develop from the east to the west extremes of the ocean, the
eastern Pacific TCs are concentrated in a limited domain centered in a
region south of Mexico. The most frequent region of genesis of named
storms is east of 16º N, 111º W, extending roughly east-to-west
between 14º N, 97º W and 15º N, 105º W. It is generally believed that
easterly waves traveling across Central America from the Caribbean are
the most frequent source of the synoptic scale vorticity maximum that
may (or may not) grow into a tropical depression or cyclone as it
progresses westward. A Costa Rican deployment site will also be
conducive for sampling more mature tropical storms and hurricanes in the
western Caribbean as well.

This location offers opportunities to continue the NASA ESE partnership
with the NOAA HRD plus two other proposed National Science Foundation
tropical cyclogenesis and hurricane rainband studies that are expected
to deploy to Acapulco, Mexico during 2005. Partnership with the NASA
Tropical Composition, Cloud, and Climate Coupling (TC-4) field study
that might also deploy to Costa Rica in 2005 will provide synergistic
opportunities to investigate tropical humidity, cloud-radiation
interactions, and the relationship of convective intensity to cloud and
precipitation microphysical processes and storm evolution. All partners
could greatly benefit from field observations collected during the
June-August time frame of 2005 using airborne assets that include high
altitude aircraft carrying remote sensing instrumentation, medium
altitude aircraft carrying remote sensors and *in situ* instrumentation,
and lower altitude aircraft carrying storm surveillance radar and *in
situ* devices to sample boundary layer conditions and air-sea
interactions. This type of collaborative study with new partners will
build yet another sturdy rung on the ladder needed to reach a greater
understanding and improved predictability of tropical cyclones. The
lessons learned during this climb will also directly contribute to the
NASA ESE mission to develop a scientific understanding of the Earth
system and its responses to change in order to improve the prediction of
climate, weather, and natural hazards.

**TABLE OF CONTENTS**

[EXECUTIVE SUMMARY 1](#executive-summary)

[1 INTRODUCTION 6](#introduction)

[1.1 Relationship of CAMEX to the NASA Earth Science Enterprise Mission
6](#relationship-of-camex-to-the-nasa-earth-science-enterprise-mission)

[1.2 Description of CAMEX Field Campaigns and Early Research Results
7](#description-of-camex-field-campaigns-and-early-research-results)

[2 NEW SCIENCE ISSUES AND MEASUREMENT STRATEGIES
8](#new-science-issues-and-measurement-strategies)

[2.1 Synoptic Scale Influences 10](#synoptic-scale-influences)

[2.2 Mesoscale Processes 12](#mesoscale-processes)

[2.3 Cloud Scale Processes 15](#cloud-scale-processes)

[3 DESCRIPTION OF NEW CAMEX FIELD OPERATIONS
17](#description-of-new-camex-field-operations)

[3.1 Climatology 18](#climatology)

[3.2 Logistics 18](#logistics)

[3.3 Potential Partnerships With NOAA, NSF, and USWRP
21](#potential-partnerships-with-noaa-nsf-and-uswrp)

[3.4 Potential Partnership With Other NASA Earth Science Teams
22](#potential-partnership-with-other-nasa-earth-science-teams)

[3.5 CAMEX-5 Measurement Priorities by Observation Platform
23](#camex-5-measurement-priorities-by-observation-platform)

[4 EXPECTED SIGNIFICANCE OF CAMEX-5
24](#expected-significance-of-camex-5)

[5 REFERENCES 25](#references)

[APPENDIX A Journal Articles That Reference CAMEX-3 or CAMEX-4 Data
26](#appendix-a-journal-articles-that-reference-camex-3-or-camex-4-data)

[APPENDIX B CAMEX-5 Measurement Priorities by Observation Platform
28](#appendix-b-camex-5-measurement-priorities-by-observation-platform)

# INTRODUCTION

## Relationship of CAMEX to the NASA Earth Science Enterprise Mission

The mission of the NASA Earth Science Enterprise (ESE) is to develop a
scientific understanding of the Earth system and its responses to
natural and human-induced changes in order to improve the prediction of
climate, weather, and natural hazards. In this role, the NASA ESE
develops scientific research and measurement strategies investigating
the land, ocean, and atmospheric components of the Earth system and
their interactions. These investigations, which cover a broad continuum
of spatial and temporal scales, focus on general research themes of
climate variability and change, the water and energy cycle, weather,
atmospheric composition, the Earth surface and interior, and carbon
cycle, ecosystem and biogeochemistry processes. These themes encompass
23 basic questions outlined by Asrar et al. (2001) as NASA ESE research
priorities needed to improve the understanding of global Earth system
variability, primary forces, response mechanisms, consequences of
change, and predictability of future change.

One of the NASA ESE investigations contributing to the climate, water,
and weather research themes is the Convection And Moisture Experiment
(CAMEX), which responds to the following subset of the 23 NASA ESE
research questions. Namely,

-   How are the global precipitation, evaporation, and the cycling of
    water changing?

-   How are the variations in local weather, precipitation, and water
    resources related to global climate variation?

-   How can weather forecast duration and reliability be improved by new
    space-based observations, data assimilation, and modeling?

CAMEX, which was primarily designed to validate satellite measurements
of moisture and to create a better understanding of the water cycle,
also places an emphasis upon studies of tropical cyclones (TC).
Utilizing NASA expertise in remote sensing and spaceborne observations,
the CAMEX tropical cyclone goals are to increase the overall
understanding of TC behavior, identify remote sensing measurements and
modeling requirements for improved hurricane predictability, and to
validate the performance of NASA spaceborne sensors to accurately
monitor the short-term impacts and long-term trends of tropical storms
and hurricanes. These goals have lead to a strong collaborative
partnership with the Hurricane Research Division (HRD) of the National
Oceanic and Atmospheric Administration (NOAA) Atlantic Oceanographic and
Meteorological Laboratory and the United States Weather Research Program
(USWRP) who have similar goals to advance the understanding and
predictability of hurricanes as part of their responsibility to expedite
the transfer of hurricane research advancements to operational
forecasting enhancements.

## Description of CAMEX Field Campaigns and Early Research Results

The centerpiece of the CAMEX effort has been a series of field research
campaigns employing spaceborne, airborne, and ground-based assets with a
particular emphasis on remote sensing observations. Four field campaigns
have been conducted during an eight-year period between 1993-2001.
CAMEX-1 conducted in 1993 and CAMEX-2 conducted in 1995 provided a
performance test bed for new airborne or ground-based instrumentation
designed to simulate or complement precipitation and moisture
observations made by satellite sensors. CAMEX-3 conducted in 1998 and
CAMEX-4 conducted in 2001 incorporated many of the early CAMEX sensors
into a larger, more complete collection of remote sensing and *in situ*
devices for a focused investigation of tropical storms, hurricanes, and
convection. These latter two experiments were based in Florida during
1998 and 2001, respectively, in order to sample tropical cyclones in the
western Atlantic Ocean basin and the Gulf of Mexico while also
supporting validation activities for the Tropical Rainfall Measuring
Mission (TRMM).

CAMEX-3 was an early opportunity for the NASA ESE and NOAA HRD to
explore the benefits of a collaborative field mission. The NASA ESE
assembled a unique array of remote sensing and *in situ* aircraft
instrumentation for the high altitude ER-2 and the medium altitude DC-8
aircraft along with ground-based radar, profiler, and radiosonde
resources. These assets were highly complementary to the radar and *in
situ* instrumentation of the NOAA P-3 aircraft. Together, the two
agencies developed joint research strategies to investigate the
interplay of hurricane inner core dynamics with the upper tropospheric
environment, map the synoptic flow environment, identify the intensity
changes of landfalling hurricanes, and sample the environment of
potential hurricane genesis conditions. The NASA / NOAA aircraft
missions proved to be a highly successful endeavor that provided
three-dimensional sampling of hurricane conditions with the NASA
aircraft focusing on the upper altitudes above 9 km and the NOAA
aircraft concentrating on the lower altitudes below 9 km.

Based upon the success of CAMEX-3, the NASA Earth Science Enterprise
collaborated with NOAA HRD again for CAMEX-4. An emphasis upon improving
modeling techniques was added to the research objectives which focused
more specifically upon observation and modeling of rapid
intensification, observation and modeling of storm movement, improving
remote sensing techniques for observing wind, temperature, and moisture
in tropical cyclones and their environment, and enhancing the
understanding of tropical convective system structure and dynamics
including scale interactions between intense convection and mesoscale
systems. The collaboration between NASA, NOAA, and the USWRP Hurricanes
at Landfall Initiative developed into an even stronger relationship
during CAMEX-4. A NOAA P-3 aircraft accompanied the NASA ER-2 and DC-8
aircraft on every priority science mission including auxiliary
thunderstorm missions in the vicinity of Key West, Florida as part of
the Keys Area Microphysics Project. This smaller project was a secondary
CAMEX objective to study thunderstorm structure, precipitation systems,
and atmospheric water vapor profiles in an effort to improve
quantitative precipitation estimates.

All together, a total of eight tropical storms and hurricanes were
investigated during the CAMEX field campaigns including Bonnie,
Danielle, Earl, and Georges during 1998 and Chantal, Erin, Gabrielle,
and Humberto during 2001. Most of these storms were sampled with
aircraft over the open ocean, but Bonnie, Georges, and Gabrielle also
provided opportunities to monitor landfalling impacts. A few of the
storms were sampled on multiple occasions during a course of several
days. Most notable of these was Hurricane Humberto, which was sampled on
three consecutive days during a cycle of both increasing and decreasing
intensity. Information collected for each of the eight CAMEX tropical
cyclones as well the TRMM validation activities have been archived and
are readily available for distribution. See
[http://camex.msfc.nasa.gov](http://camex.msfc.nasa.gov/) to access
available data.

Analysis of this information has begun to successfully address the CAMEX
research topics. As an example, Heymsfield et al. (2001) have thoroughly
examined the eyewall structure of Hurricane Bonnie and suggest that
convectively induced downdrafts may contribute as much as 3°C to a
hurricane\'s warm core. Geerts et al. (2000) describe the intense
convection that developed within the eye of Hurricane Georges due to
orographic lifting during landfall in the Dominican Republic.
Skofronick-Jackson et al. (2003) demonstrate how to estimate vertical
content and particle size distribution of hurricane hydrometeors using
CAMEX active and passive microwave airborne observations with an
iterative retrieval algorithm. Kamineni et al. (2003) discuss how high
resolution water vapor cross-sectional data contribute to improved
hurricane intensity and track forecasts. Appendix A contains a more
complete list of journal articles referencing CAMEX information.
Additional research findings are also being prepared for a special issue
of the American Meteorological Society *Journal of Atmospheric
Sciences*.

# NEW SCIENCE ISSUES AND MEASUREMENT STRATEGIES 

The success of the CAMEX research and the strong partnership forged
between NASA, NOAA, and USWRP represents a sturdy rung of the ladder
being built by many of the scientific community to reach a greater
understanding and improved predictability of tropical cyclone behavior.
Yet, many more rungs in the ladder still remain to be built. Improved
skill in prediction of TC genesis, intensity change, and rainfall
potential are just a few of these rungs requiring attention due to
deficiencies in the understanding of the physical processes involved and
additional deficiencies in numerical model parameterizations and data
assimilation inputs. The spaceborne and sub orbital observational
capabilities and technological development activities of NASA put it in
a unique position to assist the hurricane research community in
addressing these deficiencies, while also tackling NASA ESE mission goal
to understand and predict changes to the total Earth system. In
particular, the launch of several new satellites during the 2001-2005
time frame and the prospect of using uninhabited aerial vehicles (UAV)
for hurricane monitoring during the next decade offer new research tools
that need to explored and validated. Thus, the timing is right to
consider a new field phase of CAMEX to support the validation and
utilization of new satellite products while also demonstrating the
impact that higher spatial and temporal resolution airborne information
from UAV platforms might contribute to forecast improvements.

A new field phase of CAMEX could both benefit from information collected
by and contribute to the evaluation of the Aqua and Jason-1 satellites
plus the SeaWinds instrument, which were launched after the 2001 CAMEX
field phase. Aqua measures clouds, precipitation, atmospheric
temperature and moisture content among other parameters. Jason-1
monitors global ocean circulation, El Nino conditions, and ocean eddies.
SeaWinds, like its counterpart on the QuikSCAT satellite, measures sea
surface wind and direction as it flies aboard the Japanese Advanced
Earth Observation Satellite (ADEOS-II) spacecraft. CAMEX could assist
with the validation of the CloudSat, Aura, and CALIPSO satellites
scheduled for launch after 2003. CloudSat will provide radar
measurements of the vertical structure of clouds and will better detect
the upper-level outflow of hurricanes because it is more sensitive than
previous spaceborne radars. The Aura satellite will provide measurements
of the spatial and temporal variability of ozone, water vapor, and
cirrus clouds in the upper troposphere and lower stratosphere. The
Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations
(CALIPSO) will provide lidar measurements of aerosol and cloud
distributions as well as backscatter and extinction profiles through
aerosol and thin cloud layers. New partnerships with NASA ESE research
teams utilizing these new satellites ensure a more complete
understanding of tropical cyclone behavior and water cycle variability
within the context of the total Earth system.

The timing is also right to assess the gaps in knowledge that still
exist for CAMEX. Operational requirements and NASA goals for five-day
forecasts and beyond necessitate an accurate knowledge of the
contributing factors to hurricane genesis and intensity change. However,
previous CAMEX field operations have not adequately obtained
observations related to tropical cyclone genesis due to the rare
instances of these types of systems at the previous deployment
locations. Airborne measurements of cloud and precipitation properties
have led to improved microphysical parameterizations, but have also
pointed out the need for measurements at a greater variety of
atmospheric temperature levels. Numerical modeling efforts have
demonstrated a requirement for higher resolution humidity information to
drive the model convection, but additional observations in the tropical
cyclone core and synoptic environment are needed to initialize and
validate these models.

In order to contribute to the NASA ESE mission and build upon the
strengths of NASA expertise to assist the hurricane research community,
the CAMEX-4 Science Team recommends the next phase of CAMEX include a
new field campaign called CAMEX-5. This experiment would concentrate the
understanding and prediction of tropical genesis, intensity, motion,
rainfall potential, and landfall impacts by remote and *in situ* sensing
of the three phases of water from spaceborne and airborne platforms.
Hurricane behavior is a multi-scale problem: the hurricane vortex is
hundreds of kilometers in horizontal scale, but the eye and eyewall are
tens of kilometers (mesoscale), and the embedded convective clouds are
order of kilometers (cloud scale). In addition, hurricanes are heavily
influenced by phenomena in their environment that are thousands of
kilometers wide (synoptic scale). CAMEX-5 will address the broader goals
of CAMEX by specifically considering each scale of motion and how it
interacts with other scales. A specific set of questions (discussed
below) has been generated for each scale of interest.

## Synoptic Scale Influences

### General Discussion and Science Questions

The basic environmental conditions favorable for tropical cyclone
development and intensification are well known. Yet, specific processes
by which the environment produces and influences a tropical cyclone are
not as well understood. *In situ* environmental sampling is also
extremely limited in the oceanic locations where tropical cyclones
occur. Acquiring and assimilating remotely sensed data or special *in
situ* observations is necessary to improve the characterization of
relevant environmental conditions within a forecast model. This
subsequently enables improved predictions of track, intensity, and
precipitation. Better characterization of the synoptic scale environment
also enables more accurate examination of the physical processes
involved in tropical cyclone development. These issues may be addressed
by the following key questions:

1.  **What are the roles of environmental vertical wind shear in
    tropical cyclone genesis, intensification, track, and rainfall?**

Strong vertical wind shear in the environment is known to have a
detrimental effect on tropical cyclone development. Some storms seem
more susceptible to these detrimental effects than others. This may be a
function of storm intensity, size, organization; magnitude or
orientation of the shear; or other characteristics of the environment.
There are even indications that some shear may have a positive effect on
tropical cyclogenesis, through forcing and organizing downshear
convective bursts.

2.  **How does the amount and distribution of environmental moisture
    contribute to tropical cyclone genesis, intensification, track, and
    rainfall?**

Water vapor is a key element for the understanding of the processes of
precipitation, evaporation, and the release of latent heat. Most
numerical models have several limitations in the representation of these
factors due to the lack of adequate and accurate moisture measurements
with sufficient vertical and horizontal resolutions. The high-resolution
moisture data sets acquired during CAMEX made a large impact on the
numerical estimate of mass convergence and moisture fluxes during
experimental forecasts. The forecast track and intensity estimates from
the experiments show a marked improvement compared to the control
experiment where such data sets were excluded.

3.  **How do large-scale effects, such as interactions between easterly
    waves, terrain, upper-level troughs, atmospheric dust layers, and
    the Intertropical Convergence Zone, contribute to tropical
    cyclogenesis and intensity change?**

Several mechanisms have been proposed as keys to tropical cyclogenesis.
Very little is known about how a small-scale tropical depression first
emerges within a larger scale disturbance, such as an easterly wave. How
does the structure of an easterly wave change as it crosses from the
Caribbean to the Pacific? What are key differences in the structure and
environments of developing versus non-developing waves? What determines
the balance between an upper-level trough\'s positive momentum
transports and its detrimental shear? Initial studies have shown that
current forecast models do not sufficiently capture the low humidity,
static stability, and strong low-level winds of suspended atmospheric
dust layers and how the interaction of these features with tropical
cyclones or incipient disturbances impacts TC
intensification/suppression. How well can satellite measurements (e.g.,
moisture, aerosol profiles) improve remote characterization of
atmospheric dust layers and its impact on TCs?

4.  **What are the capabilities and limitations of using spaceborne and
    airborne information to improve forecasts of tropical cyclone track,
    intensity, and rainfall?**

With the launch of new satellites and the promise of suitable UAV
platforms for scientific research, new spaceborne observations and
technology should be explored and evaluated. How accurate are the
relevant satellite-based retrievals, and how are they affected by
spatial resolution? Which remotely sensed parameters are the best
indicators of intensity change? How well can TC predictions be improved
by new data assimilation inputs or targeted observations? How should a
flexible network of spaceborne and airborne observations be designed to
utilize the best capabilities of each observation type for improved TC
forecasting skill?

### Synoptic Scale Measurement Strategy

The surveillance of the synoptic scale is important since genesis does
follow from the growth of incipient disturbances. What makes some
disturbances grow and not others is still not fully understood. Only a
few instances of genesis may be observable during a CAMEX field phase,
but observing the non-developing disturbances is equally important. It
is imperative that detailed data sets of winds, temperature, moisture,
pressure, cloud cover, precipitation and the sea state are obtained. Two
general measurement domains are recommended.

Over a domain enclosing \~1000 km around a potentially suspected active
region, a data resolution of roughly 50 km in horizontal and 500 meters
in the vertical is recommended. Suitable measurements currently are
possible from airborne remote sensors for cloud, precipitation,
temperature, and humidity profiles. Wind profiles can be provided by
dropsondes, although higher temporal resolution wind profiles such as
those measured by an airborne lidar system would be also desirable.
Twice daily sampling missions would be recommended if NASA could partner
with other agency field campaigns for aircraft resources. Adaptive
observation strategies guided by numerical models, satellite
observations, and conceptual models could identify the most critical
regions for sampling by medium and high altitude aircraft. Lower
altitude aircraft with scanning Doppler radar are necessary to map the
low-level vorticity structure.

Over a domain enclosing \~5000 km, a recommended data resolution would
be 100 km in the horizontal and 1 km in the vertical. Remotely sensed
satellite and other related data assimilation products would be high
priority assets for this domain. The desired temporal sampling
resolution would be once a day.

A surface-based measuring component is also desired in order to
supplement observations of the environment and of the mesoscale
structure of waves passing through the 1000 km and 5000 km domain areas.
Fixed surface-based observations are needed to help delineate the
environment of tropical cyclones and tropical cyclone precursor
disturbances using continuous observation or at least fixed temporal
sampling. Surface-based options are not mutually exclusive; each could
stand-alone or complement the others. Some possible options are listed
below:

-   Available coastal upper air networks, ocean buoys, and ships of
    opportunity could provide information to augment the satellite
    observations of the 5000 km domain.

-   Land-based profiler, Doppler radar and/or rawinsonde sites could be
    of considerable value because they can be located to best detect
    easterly waves that provide the primary precursor disturbances for
    tropical cyclones. 

-   The NOAA Research Vessel Ron Brown, sitting at a fixed position
    would provide an excellent site for describing wave passages.  The
    ship is equipped with a C-band radar, rawinsonde system, and
    wind/precipitation profiler and could serve as a platform for many
    more *in situ* and remote sensors.

-   Ground-based lightning observations would provide a means of sensing
    the location and frequency of lightning (and hence, strong
    convection) during tropical cyclone or easterly wave passage.  These
    data have been shown to be of value in the early stages of tropical
    cyclogenesis.  Existing networks could be augmented with additional
    sensors near the deployment location or on research vessels.

In addition to the collection of synoptic scale observations, a detailed
data assimilation component will be important to the next field phase of
CAMEX in order to properly exploit the dropsonde, flight level and other
remote sensed profiling data. Assessing the utility of targeted airborne
observations for improved forecasts should be considered. Validating
satellite observations with airborne *in situ* and remotely sensed data
will also be important to improving general data assimilation procedures
for TC scenarios. Given a medium altitude aircraft flying between 9-12
km, a flight pattern can be mapped within +/- 45 minutes of satellite
overpass that could cover an area within several satellite footprints.
This flight pattern will allow a large number of independent aircraft
measurements within a single satellite footprint region so that
small-scale variability of parameters such as water vapor within the
satellite observation region could be studied.

## Mesoscale Processes

### General Discussion and Science Questions

Tropical cyclones almost always develop within larger-scale pre-existing
disturbances. In the Atlantic and eastern Pacific, the pre-existing
disturbances are typically associated with easterly waves, which have a
zonal scale of 2000-4000 km. Very little is known about how a
small-scale tropical depression first emerges and how a depression
intensifies into a tropical storm and hurricane. In the eastern Pacific,
orographic influences may provide a means to intensify vorticity on the
mesoscale through the production of lee vortices and low-level jets near
the coastline (Farfan and Zehnder 1997). However, the frequency and
extent to which orographic forcing plays a critical role is uncertain.
Tropical cyclone motion is fairly well understood and predictions of
storm tracks are consistently improving. However, we still have
relatively little understanding of the factors associated with tropical
cyclone genesis and intensity change, and predictive skill is still
quite limited. With 5-day forecasts of track and intensity now being
routinely issued, the importance of better understanding and predicting
genesis, particularly near coastal zones, becomes paramount. The key
questions are the following:

5.  **How does a surface circulation develop?**

> Mid-tropospheric cyclonic circulations are common in tropical
> disturbances, but no tropical cyclone can form until a circulation
> reaches the surface. Whether a mid-tropospheric vortex \"builds down\"
> to the surface or if a surface circulation spins up by other means is
> not known. Different mechanisms are likely at work from one genesis
> case to another, but the details of these mechanisms are not well
> understood. Convection is an essential ingredient, but what is the
> role of cumulus convection during genesis? Cumulus convection may play
> multiple, and sometimes opposing, roles in the development of a
> tropical cyclone. Typically, convection fills the planetary boundary
> layer with low-energy air via cold downdrafts, and thus opposes
> tropical cyclone development. This is one reason that tropical
> depression formation is so rare, even though easterly waves are
> common. On the other hand, convection acts to increase the vorticity
> locally and some hypotheses suggest that intensification proceeds as
> the vorticity anomalies merge, with each merger producing a
> progressively stronger and larger vortex, thereby aiding the
> development of the vortex. A central question is how convection
> evolves in such a way to reduce the negative impacts of downdrafts,
> increase the vorticity production, and thereby generate the tropical
> depression vortex. Mid-level moistening by convection may be important
> because it reduces cold downdrafts, but the details of this process
> remain uncertain.

6.  **What controls the timing, location, and intensity of convection
    and precipitation and how do these processes feedback to the
    vortex?**

> Many factors (on many scales) can control the timing, location, and
> intensity of convection and precipitation. For example, vertical shear
> is known to produce asymmetries, but its impact on the intensity and
> longevity of convection is lacking. Convective bursts are frequently
> observed within tropical cyclones, but are not necessarily directly
> correlated with changes in intensity. The causes of these bursts and
> the manner in which they impact the larger vortex remain unclear.
> Outer rainbands are sources of asymmetric heating outside of the
> tropical cyclone inner-core. The structure and evolution of rainbands
> may play an important role in vortex evolution through the generation
> of potential vorticity, production of low-energy air in the boundary
> layer via downdrafts, and the formation of secondary eyewalls leading
> to eyewall replacement cycles.

7.  **Do radiative processes and cloud-radiation interactions contribute
    to storm development and intensification?**

> Tropical cyclone core and outflow regions consist of ice cloud with
> high albedos. The bottom parts of these layers absorb heat from the
> ocean surface while the tops radiate heat to outer space. Numerical
> studies of the effects of cloud-radiation interactions suggest that
> radiative effects can significantly impact the rate of intensification
> during genesis. Radiative destabilization associated with the
> low-level clouds in the vicinity of the storms may play an important
> role in the intensification of tropical cyclones and it appears that
> the radiative cooling at the tops of low-level clouds may be more
> important than for higher level clouds. What are the magnitudes of
> radiative heating and cooling at cloud top? Does the contribution to
> cyclone intensification depend on the areal extent of cloudiness, the
> altitude, and/or the thickness of cloud layers?

8.  **How are developing and mature systems impacted by landfall?**

> Upon landfall, the cessation of surface fluxes of heat and moisture
> combined with increased surface friction acts to rapidly weaken the
> low-level tropical cyclone vortex. In some instances, such as passage
> over Florida, the Yucatan Peninsula, or Central America, a tropical
> cyclone is weakened appreciably, but upon movement back over water,
> re-intensification can occur. It is not clear, however, whether or not
> such systems reorganize in the same manner as in the genesis stage and
> over what time scales this process takes place. Also, quantitative
> precipitation forecasting for landfalling TCs is a significant issue
> due to the dramatic impact of inland flooding. A better understanding
> of warm and cold microphysical processes, environmental wind shear
> interactions, convection intensity and movement, dry air intrusions,
> and baroclinic / frontogentic processes are needed to properly address
> this issue.

### Mesoscale Measurement Strategy

Measuring the characteristics of convection will be critical to
answering each of the questions. Ideally, measurements would
characterize the three-dimensional precipitation, velocity, and
thermodynamic fields within pre-genesis and post-genesis disturbances.
Practical measurements contributing toward this ideal would include:

-   precipitation structures and maps derived from radar and radiometer
    observations

-   horizontal wind flow derived from Doppler velocities acquired by
    scanning Doppler radar (preferably dual-Doppler)

-   convective intensity and location acquired from high-resolution
    radar reflectivity, Doppler velocities and electric field /
    lightning information

-   thermodynamic and kinematic fields along and beneath the aircraft
    flight track derived from wind, temperature, pressure, and humidity
    observations acquired by *in situ* aircraft and dropsonde
    instrumentation

-   vertical profiles of humidity and temperature acquired by lidar and
    passive microwave profiler instrumentation

Other desirable measuring systems include airborne lidar to map the
winds in clear areas where Doppler radar is ineffective and a
surface-based network of Doppler radars and profilers to provide
continuous measurements during passage of a wave or during landfall of a
tropical cyclone.

Downward looking instruments onboard high altitude aircraft should be
positioned above cloud top. This allows measurement of the entire
vertical extent of the cloud and lessens safety concerns when sampling
the strongest convection. Additional measurements from lower aircraft
would be beneficial, as the aircraft will not remain precisely aligned
with each other. Electric fields should likewise be measured from above
cloud. For the required spatial coverage, dropsondes will be necessary
from multiple aircraft. Dropsondes are most desirable from the highest
altitudes in order to sample the entire troposphere. Successful
execution of convective missions using piloted aircraft will require
close coordination with low and medium altitude aircraft, as it provides
real-time horizontal mapping from quantitative weather radar. Such
coordination will also yield the necessary scanning Doppler wind
measurements, which are critical. This may require a strong reliance on
numerous dropsondes, flight level winds from a low-level aircraft, and
measurements from radiometers or scatterometers. A ground-based network
or shipborne radar could also contribute to characterizing the low-level
winds while a disturbance passes.

## Cloud Scale Processes

### General Discussion and Science Questions

Cloud scale properties, both in the liquid and ice phases, are of
significant importance to improving the representation of quantitative
precipitation forecasts in hurricane models. Although CAMEX *in situ*
and remote sensing measurements along with two decades of measurements
by NOAA aircraft have provided a wealth of information on cloud
microphysical structure and three-dimensional air motion characteristics
of hurricanes, there are still important gaps in the understanding and
knowledge of these properties. For example, although hurricane eyewall
penetrations reported on by Black and Hallett (1986, 1999) suggest that
supercooled liquid is almost nonexistent unless the updraft velocities
exceed 5 m/s, the conclusions were primarily drawn from penetrations at
temperatures above -10ºC. Furthermore, information on the cloud droplet
and hydrometeor particle size distributions and ice/liquid water content
ratios was usually unavailable, thereby limiting the ability to develop
representations of these properties for use in models. The NASA DC-8
aircraft did collect hurricane eyewall microphysical data from CAMEX-3
and CAMEX-4, but the measurements have been confined to temperatures
below -30ºC, and instruments needed to confirm the presence and amount
of liquid water were unavailable. Lastly, *in situ* data sets needed to
evaluate retrievals of cloud properties from remote sensing instruments
mounted on overflying and underflying research aircraft have not been
obtained in a systematic fashion. In response to lingering questions
about the microphysical composition and three-dimensional wind fields of
hurricanes, key questions are:

9.  **How can the representations of hurricane microphysics be improved
    through the use of *in situ* and remotely sensed microphysical
    quantities?**

> Representation of microphysical quantities and interactions is a
> considerable source of uncertainty both in cloud resolving models and
> in remote sensing retrievals. The interrelationships between the
> hydrometeor type, size, size distribution, fall velocity, height, and
> horizontal location in the cyclone or disturbance are not well known.
> These interrelationships affect particle growth, precipitation
> efficiency, and the spatial distribution of precipitation and latent
> heating/cooling due to phase changes. These microphysical properties
> are needed for reliable numerical models of ice phase hurricane
> microphysics. What roles do aerosols play in determining the cloud and
> precipitation structure of hurricanes and how do they impact
> intensity? The availability of condensation nuclei may affect droplet
> size distributions, with implications for precipitation efficiency,
> latent heating and cooling, and subsequent effects on the larger scale
> vortex through the absorption of infrared radiation. What are the
> spatial and temporal distributions of liquid water content and
> particle size distributions? How do they compare to values simulated
> by very high-resolution numerical models? Do significant amounts of
> supercooled liquid water exist at temperatures of -20° C in
> hurricanes, even at temperatures of -30ºC and below? Liquid water is a
> primary driving force in hurricane dynamics (Lord and Lord, 1988). The
> amount of liquid water available for droplet and ice particle growth
> is a controlling factor in the development of rain and ice phase
> eyewall precipitation. Quantifying and understanding this is central
> to representing precipitation formation in tropical cyclone forecast
> models.

10. **How can quantitative precipitation forecasts be improved through
    application or assimilation of remotely sensed microphysical
    quantities as well as better representations of microphysical,
    boundary layer, thermodynamic, and other processes?**

> Precipitation forecasts have little skill in hurricanes, but rainfall
> has a tremendous impact. Freshwater floods are the leading cause of
> hurricane-related deaths. How do uncertainties in representation of
> cloud scale processes (question 9) scale up to uncertainties in
> quantitative precipitation forecasts for the hurricanes?

11. **How does the release of latent heat from microphysical processes
    feedback upon the updraft and downdraft characteristics of
    hurricanes and their evolution?**

> How do particular microphysical characteristics (the numerous
> uncertainties mentioned in question 9) control the magnitude, timing,
> and spatial distribution of latent heating and cooling?

### Cloud Scale Measurement Strategy

Progress in addressing the primary cloud scale scientific questions
requires detailed measurement of hydrometeor characteristics - particle
phase, ice particle type, particle (liquid and ice) size distributions
and densities (especially in the melting layer), particle fall
velocities, liquid and total water contents. These characteristics, and
their spatial and temporal variability, depend in part on the local
temperature, relative humidity, pressure, and three-dimensional wind. It
is important to understand the hydrometeor characteristics - as revealed
by *in situ* measurements - in terms of more readily available remote
sensing measurements. Thus, the *in situ* microphysical measurements
should be co-located with remotely sensed measurements such as radar
reflectivity, brightness temperatures, and electric fields.

Necessary instrumentation includes a suite of cloud probes on aircraft
penetrating the storms at a variety of levels, with the mixed phase
region being most desirable; Doppler radars (preferably multiple
wavelengths); passive microwave radiometers (10 to 183+/-7 GHz;
preferably 6 to 640 GHz); airborne electric field mills and/or
surface-based lightning network; flight level wind and thermodynamic
instruments on the microphysics aircraft; dropsondes released from high
altitude aircraft to describe the wind structure and thermodynamic
environment; scanning Doppler radar to describe the three-dimensional
wind field.

A medium altitude aircraft such as the DC-8 would be the most practical
for obtaining *in situ* microphysical data at the middle hurricane
levels (8-12 km). A high altitude aircraft should provide coincident
remote sensing measurements from above cloud top. It is essential that
these aircraft are closely coordinated; for optimal measurements the
aircraft will be vertically stacked with each other. As in previous
CAMEX field campaigns, it should be possible to measure the particle
size distributions and observe particle habits from the medium altitude
aircraft. The instrument complement can be expanded to include
information on particle phase and condensed water content. Nadir-viewing
Doppler radar data from the medium altitude aircraft and the overflying
high altitude aircraft can be used to provide information on particle
fallspeeds. It would also be highly desirable for the medium altitude
aircraft to make microphysical measurements at temperatures as warm as
possible (approximately --20º C or above) in the convection.
Furthermore, medium altitude aircraft spirals, along with coordinated
medium and high altitude aircraft flight patterns, would provide an
optimal database, particularly for obtaining information through the
melting layer. Cloud electrification measurements could be monitored
from the plane to reduce the chance of a lightning strike to the
aircraft. Low altitude aircraft can provide *in situ* microphysical data
up to a height of about the 0º C level in the convection. It also
provides scanning Doppler radar and the onboard radar display necessary
for locating targets during a mission using piloted aircraft. The NASA
WB-57F aircraft could also make measurements of the microphysical and
radiative properties at cloud top and above using due care for flight
safety.

# DESCRIPTION OF NEW CAMEX FIELD OPERATIONS

As mentioned earlier, previous CAMEX field operations have focused on
the western Atlantic Ocean basin and the Gulf of Mexico from an aircraft
deployment location in Florida. For the next CAMEX field phase, the
CAMEX-4 Science Team recommends a Costa Rican deployment location for
the NASA aircraft. This location will be conducive to addressing all of
the science questions raised earlier in this paper while significantly
improving the opportunities for sampling tropical cyclone genesis
scenarios. The benefits of the climatology, logistics, and potential
partnerships of a Costa Rican deployment are presented below along with
recommended measurement priorities for satellite, aircraft, and
surface-based observations. Yet regardless of the location of the next
CAMEX field phase, the most crucial aspect of field success will be
joint aircraft missions conducted with high altitude aircraft carrying
remote sensing instrumentation, medium altitude aircraft carrying remote
sensors and *in situ* instrumentation, and lower altitude aircraft
carrying storm surveillance radar and *in situ* devices to sample
boundary layer conditions and air-sea interactions.

## Climatology

The eastern tropical Pacific Ocean, on average, experiences more
tropical cyclones each season than the Atlantic Ocean. In contrast to
the Atlantic, which can have TCs develop from the east to the west
extremes of the ocean, and from 10º N to 35º N, the TCs are concentrated
in a limited domain centered in a region south of Mexico.  The region of
genesis is the most concentrated one on the planet (Frank 1987, Molinari
et al. 2000). Figures 1, 2, 3, and 4 represent initial locations of
tropical cyclones (depressions, storms, and hurricanes) for June, July,
August, and September respectively during the years 1970-2002, according
to the National Hurricane Center\'s best track files. These locations
correspond to the completion of the tropical cyclogenesis process since
the genesis process has been occurring for a period of time before the
disturbances reach the plotted locations. The range rings are plotted at
400 n mi (740 km) intervals from San Jose, Costa Rica in red and from
Acapulco, Mexico in blue.

While the maximum occurrence of TCs is centered at 16º N, 111º W, the
most frequent region of genesis of named storms is east of that
location, extending roughly east-to-west between 14º N, 97º W and 15º N,
105º W. As Molinari et al.  (2000) show, the occurrence of tropical
depressions increases rapidly as one proceeds westward from the
longitudes of Central America, especially west of 95º W. Therefore, if
the target of interest is the tropical wave -to-depression transition,
this often happens between 93º-105º W, while the depression-to tropical
storm transition centers somewhat farther west, say from 95º-111º W. It
is generally believed that easterly waves traveling across Central
America from the Caribbean are the most frequent source of the synoptic
scale vorticity maximum that may (or may not) grow into a tropical
depression or cyclone as it progresses westward.

## Logistics

Much of the genesis area is accessible to aircraft basing in San Jose,
Costa Rica (10º N, 84º W), and in Acapulco, Mexico (17º N, 100º W). The
wave-to-depression transition is especially accessible to jet aircraft
based in Costa Rica, while the entire cyclone area can be reached from
Acapulco. Using a ferry speed of 400 kt (conservatively 6º of longitude
per hour), an in-storm pattern could begin at any location east of 96ºW
with a 2-hour ferry flight. Storm center locations west of 104º W
(pattern start location of 102º W) would be reachable only with a 3-hour
ferry flight. Therefore, the optimum location for a target storm is
between 93º-98º W, a frequent genesis location.

![](media/image1.png){width="4.739583333333333in"
height="3.5548611111111112in"}

Fig. 1. Initial locations of tropical cyclones (depressions, storms, and
hurricanes) for June during the years 1970-2002, according to the
National Hurricane Center\'s best track files. These locations
correspond to the completion of the genesis process. The range rings are
plotted at 400 n mi (740 km) intervals from San Jose, Costa Rica in red
and from Acapulco, Mexico in blue.

![](media/image2.png){width="4.739583333333333in"
height="3.5395833333333333in"}

Fig. 2. Same as Fig. 1 except for July

![](media/image3.png){width="4.752777777777778in"
height="3.564583333333333in"}

Fig. 3. Same as Fig. 1 except for August

![](media/image4.png){width="4.739583333333333in"
height="3.5548611111111112in"}

Fig. 4. Same as Fig. 1 except for September

For storm centers located west of about 100º W, the aircraft based in
Costa Rica could mainly supply environmental data in the eastern
semicircle, while aircraft based in Acapulco could cover the storm for
several days. For storms centered in the western Caribbean, the
situation is reversed, as aircraft based in Costa Rica can reach most
locations, but locations east of 85º W would be far from the Acapulco
base. The optimum target for joint missions from both Costa Rica and
Acapulco would be a storm approaching landfall in Belize or on the
Yucatan peninsula.

## Potential Partnerships With NOAA, NSF, and USWRP

The previous field phases of CAMEX have benefited greatly from the joint
missions with the NOAA HRD, scientifically and logistically.  The
practical aspects are obvious:  NOAA flies low, NASA flies high; NOAA
has quantitative radars for flight safety and scientific direction, NASA
does not; NOAA and NASA aircraft have different but complementary remote
sensing capabilities.  The hurricane and its precursor disturbances
extend throughout the troposphere, and together, the NOAA and NASA
aircraft have proven their ability to sample the whole storm. 
Scientifically, the long-term interests of NOAA HRD scientists in
improving the understanding of intensity change and quantitative
precipitation observations and forecasting are well matched to the
interests and capabilities of NASA investigators.  These two issues are
sufficiently challenging that they are also at the top of the priority
list put forth by the USWRP Hurricanes at Landfall Initiative.

Intensity change notably includes genesis.  Why so few tropical
disturbances intensify into depressions and then into tropical cyclones
while the majority of them remain weak is one of the most intriguing
unsolved problems in the atmospheric sciences.  It is also a major
challenge to forecasters, which explains its high priority for NASA,
NOAA, USWRP, and the National Science Foundation (NSF).  The Florida
deployment locations used previously for CAMEX worked well for
investigating hurricanes, but most of the favored genesis areas in the
Atlantic are far away from Florida.  In contrast, the genesis area is
highly concentrated in a location accessible from Costa Rica. The
essential joint missions with the NOAA aircraft are feasible if those
aircraft are also based so that they can reach the same areas, for
example Acapulco.  If the goal is to investigate and understand why some
incipient storms intensify and some do not, the combination of NOAA
basing in Mexico and NASA in Costa Rica is responsive to that goal.

In addition, there are two relevant NSF-sponsored programs proposed for
2005. These are the second Tropical Experiment in Mexico (TEXMEX II) and
a hurricane rainband experiment, which require cooperation with the NOAA
HRD as well as participation of the NOAA P-3s and the ELDORA radar
onboard the Naval Research Laboratory P-3. The spatial resolution of the
ELDORA makes it a tremendous asset for mapping the precipitation and
wind in joint missions with CAMEX.  Likewise, TEXMEX II is specifically
designed for the genesis areas for the same reason that is proposed for
CAMEX-5:  that is the most concentrated genesis region on earth, and it
is accessible from an Acapulco base.  The hurricane rainband experiment
could be done from any base that can reach mature hurricanes, including
Acapulco.  Given sufficient flight hour resources, therefore, the
objectives of all four programs can be reached with an Acapulco base for
the P-3s and a Costa Rica base for the NASA aircraft. The joint lessons
learned from this type of partnership could be invaluable to the general
hurricane community.

## Potential Partnership With Other NASA Earth Science Teams

In addition to partnerships with other hurricane studies, the NASA ESE
could also benefit from CAMEX partnerships with other NASA Earth Science
research teams. One is Tropical Composition, Cloud, and Climate Coupling
(TC-4), which is another NASA ESE investigation with several planned
field phases. The primary goals of TC-4 are to gain a better
understanding of chemical, dynamical, and physical processes occurring
in the tropical upper troposphere and in the layer surrounding the
tropical tropopause as well as the roles that the anvils of deep
convective clouds and tropical cirrus play in humidifying the upper
troposphere and lower stratosphere. These issues are relevant to studies
involving global climate change, stratospheric ozone depletion, global
tropospheric chemistry, and the Earth's radiation balance. The key
questions TC-4 seeks to answer are:

1)  What mechanisms maintain the humidity of the stratosphere? What are
    the relative roles of large-scale transport and convective transport
    and how are these processes coupled?

2)  What are the physical mechanisms that control (and cause) long-term
    changes in the humidity of the upper troposphere in the tropics and
    subtropics?

3)  What controls the formation and distribution of thin cirrus in the
    Tropical Tropopause layer, and what is the influence of thin cirrus
    on radiative heating and cooling rates, and on vertical transport?

4)  What are the chemical fates of short-lived compounds transported
    from the tropical boundary layer into the Tropical Tropopause layer?
    (i.e., What is the chemical boundary condition for the
    stratosphere?)

5)  What are the mechanisms that control ozone within and below the
    Tropical Tropopause Transition layer?

6)  How do convective intensity and aerosol properties affect cirrus
    anvil properties?

7)  How do cirrus anvils, and tropical cirrus in general, evolve over
    their life cycle and how do they impact the radiation budget and
    ultimately the circulation?

8)  How can space-based measurements of geophysical parameters,
    particularly those known to possess strong variations on small
    spatial scales (e.g., H~2~O, cirrus), be validated in a meaningful
    fashion?

In order to address these questions, the TC-4 Science Team has expressed
an interest in partnering with CAMEX during a Costa Rican deployment as
one of several TC-4 field campaigns planned for the next several years.
The TC-4 research goals to investigate the mechanisms controlling upper
tropospheric and stratospheric humidity of the tropics meshes very well
with the CAMEX-5 interest in studying the details of how environmental
moisture contributes to tropical cyclone behavior. Both TC-4 and CAMEX-5
have synergistic interests in radiative processes, cloud-radiation
interactions, and the relationship of convective intensity to cloud
microphysical processes and storm evolution. TC-4 sampling targets will
include mesoscale convective systems that are common in the genesis
region that would benefit both scientifically and logistically from a
partnership with P-3 aircraft equipped with storm surveillance radar. 
Field observations collected during the June-August time frame of 2005
would be beneficial to the goals of both CAMEX and TC-4. Sharing
logistics expenses could provide a cost savings for NASA while also
increasing the utility of the aircraft. During possibly inactive periods
in the TC genesis region, an alternate target for the TC-4 aircraft is
present almost every other day in the Gulf of Panama, which is easily
reached from Costa Rica. As with the other potential CAMEX partnerships,
the opportunities for synergistic discoveries between CAMEX and TC-4
could be invaluable to the scientific community.

Partnerships could also be developed with several NASA ESE satellite
teams who could utilize CAMEX data for validation purposes or who could
supply new satellite products benefiting the TC research of CAMEX-5. One
such partnership might be with the Atmospheric Infrared Sounder (AIRS)
Validation Team. The AIRS provides measurements of atmospheric
temperature and humidity; land and sea surface temperatures; cloud
properties; radiative energy flux from the Aqua satellite. Current
validation efforts have demonstrated that the AIRS is currently able to
achieve its specified retrieved temperature uncertainty of 1 K in 1 km
layers under most cloud conditions. However, reducing the uncertainties
for other retrieved quantities remains a challenge for a number of
reasons. Future CAMEX observations could help resolve some of these
sources of uncertainty in AIRS retrievals. Useful observations would be:

-   Observations of cloud state, such as cloud coverage and cloud top
    pressure and temperature, to help diagnose the AIRS cloud clearing
    procedure and associated errors.

-   Fine-scale observations of water vapor and temperature distributions
    including upper tropospheric humidity to help constrain and diagnose
    the AIRS water vapor retrieval errors.

## CAMEX-5 Measurement Priorities by Observation Platform

Appendix B lists the measurement priorities by observation platform for
the recommended CAMEX-5 observations. This table demonstrates how
various measurements serve several purposes although the priorities may
shift between the three different scales of study. All measurements
mentioned in Section 3 have been combined, for the sake of brevity, into
nine general categories. For example, aircraft radar and passive
microwave observations of rainfall have been combined into high priority
precipitation measurements addressing the mesoscale research questions.
Dropsondes measurements are considered *in situ* aircraft observations
for the purpose of this table.

# EXPECTED SIGNIFICANCE OF CAMEX-5

The most significant aspects of a new field phase for CAMEX will be the
comprehensiveness of the research and the strength of the collaborative
partnerships. Addressing the CAMEX-5 synoptic scale questions will lead
to a better understanding of tropical cyclone behavior within the
context of the large scale environment. The CAMEX observations and
measurement strategies pertaining to data assimilation and adaptive
observations will identify optimal ways to characterize this large scale
environment. The mesoscale questions, indeed the questions at all
scales, contribute to understanding the mechanisms by which a small
fraction of tropical disturbances develop into tropical cyclones that
might have significant weather impacts on society. Success in addressing
the cloud scale questions will result in better parameterizations of all
phases of water in numerical models. Besides contributing to more
accurate precipitation forecasts, these improvements have implications
for the modeled storm dynamics by enhancing parameterizations of latent
heating/cooling and water loading. The coupling of detailed
microphysical observations together with remote sensing measurements
will also lead to superior remote sensing retrievals that will in turn
yield more accurate quantitative precipitation estimations.

The CAMEX-5 emphasis to address the understanding and prediction of
tropical genesis, intensity, motion, rainfall potential, and landfall
impacts by remote and *in situ* sensing of the three phases of water
from spaceborne and airborne platforms will allow multiple aspects of
the water cycle to be examined as well. Incorporating results from the
tropical cyclone studies into the broader context of water cycle
variability and responses to change will contribute directly to a
greater knowledge of the relationships and interactions of the total
Earth system. Similarly, a partnership with the TC-4 will provide
synergistic opportunities relevant to broader studies of global climate
change, stratospheric ozone depletion, global tropospheric chemistry and
the Earth's radiation balance due to the TC-4 emphasis on studies of
chemical, dynamical, and physical processes of the upper troposphere and
stratosphere.

CAMEX-5 will also provide numerous opportunities to validate current
NASA observational capabilities and remote sensing retrievals or to
develop new retrieval applications or concepts for new technologies. For
example, observational capabilities or strategies tested during CAMEX-5
could eventually be deployed on routine UAV missions of the future as
part of a flexible observational network monitoring critical weather
events such as hurricanes using both spaceborne and suborbital
platforms. The collaborative nature of CAMEX-5 with multiple
governmental and academic partners will ensure that newly developed
applications or technologies are pertinent and relevant to a broad
spectrum of users. Thus, CAMEX-5 will both provide and promote the use
of NASA technological capabilities to assist the general hurricane
research community to advance toward more accurate and dependable
tropical cyclone predictions. Lessons learned from this activity will
directly contribute to the NASA ESE mission to develop a scientific
understanding of the total Earth system and its responses to change in
order to improve the prediction of climate, weather, and natural
hazards.

# REFERENCES

Asrar, Ghassem, Kaye, Jack A, Morel, Pierre. 2001: NASA Research
Strategy for Earth System Science: Climate Component: *Bull. of the
Amer.* Meteor. Soc., **82**, 1309-1330

Black, R.A., Hallett, J. 1986: Observations of the Distribution of Ice
in Hurricanes. *J. Atmos. Sci.*, **43**, 802--822.

Black, Robert A., Hallett, John. 1999: Electrification of the Hurricane.
*J. Atmos. Sci*., **56**, 2004--2028.

Farfán, Luis M., Zehnder, Joseph A. 1997: Orographic Influence on the
Synoptic-Scale Circulations Associated with the Genesis of Hurricane
Guillermo (1991). *Mon. Wea. Rev*., **125**, 2683--2698.

Geerts, Bart, Heymsfield, Gerald M., Tian, Lin, Halverson, Jeffrey B.,
Guillory, Anthony, Mejia, Mercedes I. 2000: Hurricane Georges\'s
Landfall in the Dominican Republic: Detailed Airborne Doppler Radar
Imagery. *Bull. of the Amer. Meteor. Soc.*, **81**, 999--1018.

Heymsfield, Gerald M., Halverson, Jeffrey B., Simpson, Joanne, Tian,
Lin, Bui, T. Paul. 2001: ER-2 Doppler Radar Investigations of the
Eyewall of Hurricane Bonnie during the Convection and Moisture
Experiment-3. J. *Appl. Meteorol*., **40**, 1310--1330.

Kamineni R, T.N. Krishnamurti, R.A.Ferrare, S. Ismail, E.V. Browell,
2003: Impact of high resolution water vapor cross-sectional data on
hurricane forecasting, *Geophy. Res. Lett.,* **30**,1234.

Lord, Stephen J., and J.M.Lord, 1988: Vertical Velocity Structures in an
Axisymmetric, Nonhydrostatic Tropical Cyclone Model. *J. Atmos. Sci.,*
**45**, 1453--1461.

Molinari, John, Vollaro, David. 2000: Planetary- and Synoptic-Scale
Influences on Eastern Pacific Tropical Cyclogenesis. *Mon. Wea. Rev.*,
**128**, 3296--3307.

Skofronick-Jackson, Gail M., Wang, James R., Heymsfield, Gerald M.,
Hood, Robbie, Manning, Will, Meneghini, Robert, Weinman, James A. 2003:
Combined Radiometer--Radar Microphysical Profile Estimations with
Emphasis on High-Frequency Brightness Temperature Observations. *J.
Appl. Meteorol.*, **42**, 476--487.

# APPENDIX A Journal Articles That Reference CAMEX-3 or CAMEX-4 Data {#appendix-a-journal-articles-that-reference-camex-3-or-camex-4-data .unnumbered}

Blackwell W.J., J.W. Barrett, F.W.Chen, R.V. Leslie, P.W. Rosenkranz,
M.J. Schwartz,

and D.H. Staelin, 2001: NPOESS aircraft sounder testbed-microwave (NAST-

> M): Instrument description and initial flight results, *IEEE. T.
> Geosci. Remote,* **39**, 2444-2453.

Durden S.L., L.Li, E. Im, and S.H.Yueh, 2003: A surface reference
technique for

> airborne Doppler radar measurements in hurricanes, *J. Atmos. Oceanic
> Technol.,* **20**, 269-275.

Durden S.L., E.Im, Z.S.Haddad, and L, Li, 2003: Comparison of TRMM
precipitation

radar and airborne radar data. *J. Appl. Meteorol.,* **42** ,769-774.

Durden, S.L.2003: Airborne polarimetric radar measurements of rainfall,
*IEEE. T.*

*Geosci. Remote,* **41,** 2125-2127.

Geerts, Bart, Heymsfield, Gerald M., Tian, Lin, Halverson, Jeffrey B.,
Guillory, and

> Anthony, Mejia, Mercedes I. 2000: Hurricane Georges\'s Landfall in the
> Dominican Republic: Detailed Airborne Doppler Radar Imagery. *Bull. of
> the Amer. Meteor. Soc.,* **81**, 999--1018.

Heymsfield, Gerald M., J.B. Halverson, J. Simpson, L. Tian, and T.P.Bui,
2001: ER-2

> Doppler Radar Investigations of the Eyewall of Hurricane Bonnie during
> the Convection and Moisture Experiment-3. *J. Appl. Meteorol*.,
> **40**, 1310--1330.

Heymsfield Gerald M., B.Geerts B, and Tian L, 2000: TRMM precipitation
radar

> reflectivity profiles as compared with high-resolution airborne and
> ground-based radar measurements. *J. Appl. Meteorol*., **39**,
> 2080-2102.

Kamineni R, T.N. Krishnamurti, R.A.Ferrare, S. Ismail, and E.V.
Browell,2003: Impact

> of high resolution water vapor cross-sectional data on hurricane
> forecasting, *Geophy. Res. Lett.,* **30**,1234.

Mecikalski J.R.,2003: A method for estimating momentum fluxes of deep
precipitating

convection using profiling Doppler radar, *J. Geophys. Res-Atmos.,*
**108**.

Rizvi S.R.H., E.L.Bensman, T.Kumar, A. Chakraborty, and T.N.
Krishnamurti, 2002:

> Impact of CAMEX-3 data on the analysis and forecasts of Atlantic
> hurricanes. *Meteorol. Atmos. Phys.,* **79**, 13-32.

Sadowy G.A., A.C.Berkun, W. Chun, E. Im, and S.L.Durden, 2003:
Development of an

advanced airborne precipitation radar, *Microwave J.,* **46,** 84-98.

Skofronick-Jackson, Gail M., Wang, James R., Heymsfield, Gerald M.,
Hood, Robbie,

> Manning, Will, Meneghini, Robert, and Weinman, James A. 2003: Combined
> Radiometer--Radar Microphysical Profile Estimations with Emphasis on
> High-Frequency Brightness Temperature Observations. *J. Appl.
> Meteorol.*, **42**, 476--487.

Skofronick-Jackson G.M., A.J. Gasiewski, and J.R.Wang, 2002: Influence
of

> microphysical cloud parameterizations on microwave brightness
> temperatures. *IEEE. T. Geosci. Remote*, **40,** 187-196.

Tratt D.M., R.T. Menzies, M.P.Chiao, D.R. Cutten, J. Rothermel, R.M.
Hardesty, J.N.

> Howell, and S.L.Durden, 2002: Airborne Doppler lidar investigation of
> the wind-modulated sea-surface angular retroreflectance signature.
> *Appl. Optics,* **41**, 6941-6949.

Whiteman D.N., K.D.Evans, B. Demoz, D.O. Starr, E.W.Eloranta, D.Tobin,
W. Feltz,

> G.J. Jedlovec, S.I. Gutman, G.K.Schwemmer, M.Cadirola, S.H. Melfi, and
> F.J.Schmidlin, 2001: Raman lidar measurements of water vapor and
> cirrus clouds during the passage of Hurricane Bonnie. *J. Geophys.
> Res-Atmos*. **106**, 5211-5225.

# APPENDIX B CAMEX-5 Measurement Priorities by Observation Platform {#appendix-b-camex-5-measurement-priorities-by-observation-platform .unnumbered}

+------------------+------------+------------+------------+------------+
| **CAMEX-5**      | **S        | **         | **         | *          |
|                  | atellite** | Aircraft** | Aircraft** | *Surface** |
|                  |            |            |            |            |
|                  |            | *In situ*  | *Remote    |            |
|                  |            |            | Sensor*    |            |
+------------------+------------+------------+------------+------------+
| **SYNPOTIC       |            |            |            |            |
| SCALE**          |            |            |            |            |
+------------------+------------+------------+------------+------------+
| Precipitation    | high       | low        | high       | medium     |
+------------------+------------+------------+------------+------------+
| Moisture         | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Temperature      | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Pressure         | low        | high       | low        | high       |
+------------------+------------+------------+------------+------------+
| Wind             | high       | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Cloud State      | high       | medium     | medium     | medium     |
+------------------+------------+------------+------------+------------+
| Sea State        | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Cloud Physics    | low        | low        | low        | low        |
+------------------+------------+------------+------------+------------+
| Electric Fields  | low        | low        | low        | medium     |
| / Lightning      |            |            |            |            |
+------------------+------------+------------+------------+------------+
| **MESOSCALE**    |            |            |            |            |
+------------------+------------+------------+------------+------------+
| Precipitation    | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Moisture         | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Temperature      | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Pressure         | low        | high       | low        | high       |
+------------------+------------+------------+------------+------------+
| Wind             | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Cloud State      | high       | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Sea State        | high       | high       | high       | high       |
+------------------+------------+------------+------------+------------+
| Cloud Physics    | med        | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Electric Fields  | high       | high       | high       | medium     |
| / Lightning      |            |            |            |            |
+------------------+------------+------------+------------+------------+
| **CLOUD SCALE**  |            |            |            |            |
+------------------+------------+------------+------------+------------+
| Precipitation    | high       | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Moisture         | low        | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Temperature      | low        | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Pressure         | low        | high       | medium     | medium     |
+------------------+------------+------------+------------+------------+
| Wind             | low        | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Cloud State      | high       | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Sea State        | low        | low        | low        | low        |
+------------------+------------+------------+------------+------------+
| Cloud Physics    | medium     | high       | high       | medium     |
+------------------+------------+------------+------------+------------+
| Electric Fields  | high       | high       | high       | medium     |
| / Lightning      |            |            |            |            |
+------------------+------------+------------+------------+------------+