# Presentation: 024029

## Temperature Measurements 

**Temperature Measurements **

**Kevin E Trenberth**
**National Center for Atmospheric Research**
**Boulder CO**

## Surface Temperatures

**Ocean: thermometers; sea surface T**
**Plus IR satellite patterns**
** **
**Coverage:**
**  ****Increases over time (poor 1800s, better after 1950)**
**  ****Global after 1982 with satellite **
**  ****No Antarctica pre-IGY (1957)**
**  ****Poor southern oceans**

** ****Biases:**
**  ****Changes in observing practices**
**  ****Land use/urbanization effects**
**Advantages:**
**Long record**
**Many independent measurements**
**Several independent analyses**
**Many cross checks (NH vs SH; rural vs urban;**** ****global vs land-based vs SST vs Marine Air T)**
** **
**    ****Disadvantages:**
**Mostly less than global coverage**
**Coverage changes with time**

**Assessment:**
**Trends robust; may be slightly underestimated owing to under-representation of southern oceans and Antarctica**

_**Surface Temperatures**_

##  Coverage: 

**Begin mid-1940s**
**At best twice daily**
**Changed to 00,12 UTC July 1957**
**Marginal before 1964**
**Good vertical resolution**

**Biases: **
**Many changes in instrumentation, observing methods**
**Not designed for climate monitoring**
**Poor, no documentation of changes**
**Known biases in some brands, **
**   ****radiation effects**
**Many suspected biases not known**
**Advantages:**
**Each sounding uses new instrument  **
**Dozens of instrument types**
**Few groups, independent analyses**
**Prospects to improve record**
**Disadvantages:**
**Dozens of instruments, not calibrated**
**Biases change, often unknown**
**Spotty, non-global coverage**
**Inadequately exploited to date**

** ****Assessment:**
**Tropospheric temperature record reasonably well established for extratropics of NH after 1964.  Coverage inadequate and discontinuities serious elsewhere.**

_**Radiosonde Temperatures**_
**Thermisters, balloon borne, transmitted**

##      Satellite Temperatures (Microwave Sounder)

**9+ different satellites/instruments**
**Orbital decay affects retrieval**
**East-west orbital drift aliases diurnal cycle onto trends**
**Instrument calibration **
**Solar heating of platform**
**Retrieval amplifies noise**

**Advantages:**
**Measurement: excellent long term stability**
**Global, fairly uniform, coverage**
**Biases OK if adequate satellite overlap**
**Millions of observations (beats down noise)**
**Disadvantages:**
**Signal includes 20% from surface (land)**
**Contamination by precipitation-sized ice**
**Biases change, not reduced by averaging**
**Continuity across satellites: NOAA 9**
**Was one group (mainly) processing data**
**2nd group results differ for trends.**

**Assessment:**
**Excellent for spatial coverage, interannual variability, but suspect for trends**

_**     **__**Satellite Temperatures (Microwave Sounder)**_
**Oxygen emits microwave radiation, measured by MSU; proportional to T.  Retrieval to get 2LT record combines off-nadir and nadir footprints.**

**Coverage:**
**Global over several days**
**Began December 1978**
**2 or 4 times per day **
**(1 or 2 satellites)**
**Obs times vary with **
**   ****satellite and orbit drift**
**Very broad vertical layers**

## Satellite based observations

** ****Satellites typically last 3-5 years and have to be replaced**
** ****Orbits decay**
** ****Equator crossing times change**
** ****New satellite orbits differ**
** ****Instrument calibrations drift and can be changed by launch**
** ****Interference can occur from other instruments**

** ****Need is for stable orbits**
** ****May require boosters**
** ****Need sufficient sampling of diurnal cycle**
** ****Launch on schedule, not on failure, to ensure overlap**
** ****Calibrations required**
** ****Ground truth validation required**

## Lonnie Thompson’s tropical ice cores in Africa, southern Asia and South America have clearly shown melting and ablation coincident with the time of the satellite record.

**Lonnie Thompson**’s tropical ice cores in Africa, southern Asia and South America have clearly shown melting and ablation coincident with the time of the satellite record.

- Kilimanjaro

## Examples of surface wintertime inversion

- Examples of **surface wintertime inversion**
- and **trade wind inversion**
- which isolate troposphere from surface.

## Chapter 3.3:

- Does not deal fully with **vertical structure of atmosphere.**
- Issues include the **forcings**** **(volcanoes, GHGs, aerosols, ENSO, ozone depletion) and **response** of atmosphere to these.
-  Need to be able to simulate observed record within bounds of predictability.  Can then take it apart.   For the past 20 years, two exceptional El Niño events and two major volcanic eruptions means that specified SSTs are required, not coupled models.
- There is **no reliable baseline**** **against which to reference measurements.
- Radiosonde records can be improved using reanalysis feedback files.

## Key issues:  What is the vertical structure of climate change in the atmosphere, and how well do models reproduce it?

**Surface vs low troposphere**
-  How do they covary regionally?
-  Is the trade wind inversion at the right level in models and does it vary as observed?
-  Are wintertime surface inversions over mid-latitude continents simulated, and how do they show up in the satellite record?
-  Are warmings found in tropical glaciers present in radiosonde and satellite records?
-  Is static stability in models maintained correctly?    (relates to sub-grid scale parameterization of convection and mixing)

**Tropopause**
- Is the tropopause simulated at the correct level with the annual cycle and are changes over time and with ENSO replicated?
**Lower stratosphere**
- How well is ozone and its heating simulated?
- Is transition of warming near surface to cooling in stratosphere with changes at right level in models?

## Forcings:

**Greenhouse gases, stratospheric ozone depletion, tropospheric aerosols (scattering, absorbing, CCN), volcanic/stratospheric aerosols, clouds, water vapor.**
- Is the observed warming in the lower stratosphere with volcanic eruptions simulated?
- What is the greenhouse effect of the aerosol and the heating?
- Is the vertical profile different in regions with absorbing aerosols?
-  How much of that is because of no rain vs the aerosol effects?
- Why do the cooling effects of ozone depletion appear to penetrate into upper troposphere and is this modeled?
- Do changes in clouds, from aerosols or climate change, affect vertical temperature profiles, and are they simulated?
- Can we detect the changes in the troposphere and lower stratosphere and attribute to forcings?
**It is NOT just greenhouse gas forcing expectations that should be compared with observed!**