# Presentation: 200385

## Proposed 2007 Field Campaign

*Atmospheric Sciences Program *
*First Annual Science Team Meeting*
*Charleston, South Carolina*
*January 25-27,2005*

*National Oceanic and Atmospheric Administration*
*Climate Monitoring and Diagnostics Laboratory*
*Boulder, CO*

*Pacific Northwest National Laboratory*
*Atmospheric Chemistry and Meteorology Group*
*Richland, WA*

## Motivation

- Preferential removal of aerosols by clouds will modify aerosol properties (e.g., PM mass, size distribution, and scattering and absorption efficiencies)
- corresponding changes to primary aerosol radiative forcing
- These changes will be most apparent in the vicinity of shallow, non-precipitating cumuliform clouds
-  pump fields of newly formed aerosols from the boundary layer to the free atmosphere.
-  Once in the free atmosphere, such aerosols would then be subject to long range transport,
-  increase in the geographical domain over which they would affect radiative properties of the atmosphere.

## What type of campaign?

- From Atmospheric Sciences Program RFP:
- “...highly intensive atmospheric, process-oriented studies to test specific hypotheses about aerosol-radiative interactions.”

## 2007 Aerosol Outflow Campaign

*x*

*z *(km)

- 1

- 0.5

- 0.0

## Sampling Strategybased on cloud ensemble statistics

- Sampling Strategy**based on cloud ensemble statistics**

- Looking straight down on generic flight plan:

- Lateral/cross section of generic flight plan:

- Mean Wind

- A'

- C'

- B'

- (A) Plan View

**Notes:**
 Illustration of sampling strategy for a field of randomly distributed fair-weather cumuli. (A) Plane view, showing a schematic view as though seen from above, with randomly distributed fair-weather cumuli (shaded circles) and three legs. B) Cross section, showing sampling paths below, within and above clouds (shaded), done along each of the legs indicated in the top schematic. Thick arrows indicate sampling legs and thin arrows represent other aircraft maneuvers. 

## Which aerosols were processed by clouds?

- Use thermodynamic tracers that are conserved as air is lifted from boundary layer, saturates and exits from cloud, i.e.
**Total water mixing ratio (=vapor + liquid)**
**Equivalent potential temperature**
**Liquid-water potential temperature**
**Mixing diagrams of conserved quantities**

**Notes:**
In one application of the conserved variable diagram for a cloudy boundary layer, observations of  or  are plotted as a function of (Figure 4).  Air that consists of a mixture containing boundary-layer air, which we would expect for air parcels that emerge from a cloud, will lie on a line connecting the boundary-layer thermodynamic properties and the mean cloud-layer properties. The relative location of an observation on the mixing line indicates the proportion of air from each source region for that parcel. Air that does not lie on or near the mixing line did not originate in the boundary layer and was not processed by clouds. Measurements taken in conjunction with these points are assumed to have a similar boundary layer source. In general,  is difficult to measure in the cloud, but we only need accurate measurements below and outside of the clouds to determine if air has been processed by clouds. In addition to thermodynamic variables, measurements of atmospheric non-soluble gas concentrations can be used to indicate the source region of air parcels. 

## White PaperProposed for Posting on ASP Web Site

**“****We therefore propose to use the G-1 aircraft during the summer of 2007 to characterize **aerosol size, composition and optical properties at the base, within and above fields of fair weather cumulus at various distances downwind of a major urban source.  We anticipate...”

- “Objectives for an ASP Field Campaign to Study Aerosol Processing in Cumuliform Clouds”
- Carl Berkowitz, John Ogren, others??
- PNNL, NOAA/CMDL, others??

- White PaperProposed for Posting on ASP Web Site

## Some Criteria for Site Selection

**An isolated city**
**no major pollution sources or complex land features within ~100-200 km**
**Why St. Louis?**
**Relatively high frequency of cumuliform clouds**
**size and relative isolation,**
**history beginning in the 1970's of successful urban plume studies,**
**the NOAA/CMDL long-term measurement record of aerosol chemical and radiative properties in Bondville, IL (230 km northeast of St. Louis),**
**the planned deployment by NOAA of a light aircraft to monitor the vertical profiles of aerosol chemical, microphysical, and radiative properties in the vicinity of Bondville for a multi-year period beginning in late 2005.**

**Would welcome discussions with other ASP investigators about alternative locations...Denver, Houston, Miami...??**

## Scientific Objectives

***“...******to quantify and explain mechanisms by which the optical properties of fresh aerosols change with passage from the boundary layer into the free atmosphere through cumuliform clouds*****. “**
***A) What do we see?***
**what is the vertical and horizontal variability in aerosol absorption and scattering over regions occupied primarily by cumuliform clouds? What are the differences in these properties below and above cumulus clouds? **
***B) Why do we see it?***
**Can we reproduce the statistical properties of outflow aerosols using detailed process models?**
***C) How do we parameterize it for use in regional-scale models?***
**How can we describe these processes in a computationally efficient manner?**
*********Other objectives and scientific questions?*********