# Presentation: 723648

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

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

**Insights from **
**global analyses into **
**vertical temperature changes**

## Why should we expect surface temperatures to be related to those aloft?

## Trade wind inversion

- which isolates troposphere from surface.

- 16
- 14
- 12
- 10
-  8
-  6
-  4
-  2
-  0

-   -80  -60  -40  -20     0    20   40
-                    Temperature C

- km

- Sharp discontinuities are NOT resolved by satellite IR and Microwave radiances that cover broad layers

***Ozone layer***
***Stratosphere***
***Tropopause***
***Troposphere***
***	******Surface temperature***

## Examples of surface wintertime inversion

- and trade wind inversion
- which isolate troposphere from surface.

## Key issues

- Where on Earth is there a good local connection between temperatures at the surface and in the troposphere- nowhere is there a local heat balance?
- The links are non local:
- Regions of subsidence (inversions) have complete disconnect
- In regions of convection: low level convergence, moisture convergence, upper level divergence: vertical profile depends on moisture (from afar) and latent heating
- Local heating is NOT manifested in temperature rise but instead causes vertical motions, adiabatic cooling, and warming in the subsidence branch
- Where subsidence occurs is determined by available cooling (mostly dynamical)

## Hadley circulation and heat budget in subtropics

**    ****Ocean heat **
** ****transport**

**Dynamical cooling by advection**

**Dynamical warming by subsidence**

**Radiation**
**solar down**
**infrared up**

_**Hadley circulation and heat budget in subtropics**_

**Latent heating in convective rain**

**warm**

**Heat transport**
**by transients**

- Trenberth and Stepaniak 2003, J Climate

## Key issues

**The use of global means averages over many regions and many processes and is not very useful for resolving perceived discrepancies.**
**Recommendation: focus on regions and physically-based expectations**

## Annual anomalies for surface and MSU-2 from UAH and RSS

**Annual anomalies for surface and MSU-2 from UAH and RSS**

## Updated from Hurrell and Trenberth 1996

## Correlation of surface with MSU-2 locally for monthly anomalies

**Correlation of surface with MSU-2 locally for monthly anomalies**

- Updated from Hurrell and Trenberth 1996

## Correlation of monthly anomalies with global mean temperature

- Updated from Hurrell and Trenberth 1996

## Regression of monthly anomalies with global mean temperature

## From Hurrell and Trenberth 1998

## Key issues

**The use of linear trends is always inappropriate.  They depend critically on end points and are not robust to small changes in length of record.  Nor are they a reasonable null hypothesis for climate change.**
**Recommendation: **
**	****Focus on robust time filters **

## Fitting various straight lines does not produce a good fit.

**xxx**         0.210
-                0.155
-        **xxx**  0.149

- Courtesy M. Mann

## MSU-2 pentad Temperatures from Vinnikov and Grody (2003)

- Top: trend and total
- Bottom: detrended anomalies

- 18 pentad overlap NOAA-9 to NOAA-10

##      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**
**2****nd**** and 3****rd**** 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**

## Reanalyses

## Comparison of miscellaneous products:               Puzzling changes at 100 mb in late 2000 in METO and NCEP reanalyses /CDAS:

**Comparison of miscellaneous products:               Puzzling changes at 100 mb in late 2000 in METO and NCEP reanalyses /CDAS:**
- In UKMO: Change in assimilation system Nov 2000
- In NCEP???
- TOVS ceased and
- ATOVS NOAA-16 started 27 Feb 2001???
- 		        Bill Randel 2003

- Temp anomalies 10N-10S

## As well as puzzling changes at 100 mb in late 2000 in reanalyses /CDAS there are weird values at 850 mb: Too warm in 2002

**Subtropical trade-wind inversion???**
- 		      Bill Randel 2003

## Slide 21

## Evidence of spurious diurnal cycle  in sonde before mid 1980s?

## Trends and interannual variability

**Trends and interannual variability**

**ERA-40**

## Global monitoring

**Land**

**Sea**

**ERA-40**

**Jones et al.**
**(2001)**

**Parker et al.**
**(1995)**

**Folland et al. (2002)**

**Global monitoring**

## Anomalies in 2m temperature and 500hPa height

**o****C**

**Trends and interannual variability**

## Trends and interannual variability

**Image produced by Remote Sensing Systems and sponsored by NOAA Climate and Global Change Program**

**Time series of MSU-2 brightness-temperature anomaly (K), from Wentz and colleagues**
**Courtesy Adrian Simmons**

**Trends and interannual variability**

**Global-mean ERA-40 500hPa temperature**

## Trends and interannual variability

**Mean ERA-40 500hPa temperature**

**Northern hemisphere extratropics**

**Tropics**

**Southern hemisphere extratropics**

## Trends and interannual variability

**Global-mean ERA-40 70hPa temperature**

**Trends and interannual variability**

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## Tropics 23.5N-23.5S Courtesy Adrian Simmons

## 			ERA-40 T Trends 1979-2001; 1958-2001

- Courtesy Adrian Simmons

- 			**ERA-40 T Trends 1979-2001; 1958-2001**
**	****	****1000****	****	****	****700****	****	****	****500**
**Global**
**NH**
**Tropics**
**SH**
**	****	****300****	****	****	****200****	****	****	****100**
**Global**
**NH**
**Tropics**
**SH**

## Linear T trends ERA40 1979-2001

_**level**__**	**__**     Globe**__**	**__**NH**__**	**__**Tr**__**	**__**SH**_
- 1000  		0.3	0.7 	0.2	0.2
-  925		0.3	0.7	0.3	0.2
-  850		0.4	0.7	0.4	0.3
-  775		0.4	0.6	0.2	0.3
-  700		0.2	0.5    -0.2	0.3
-  600		0.1	0.4    -0.3	0.3
-  500		0.1	0.4    -0.3	0.3
-  400		0.2	0.4    -0.3	0.5
-  300		0.5	0.6     0.2	0.7
-  250		0.5	0.3	0.7	0.4
-  200		0.3	0.0	1.3     -0.3
-  150		0.2	0.1	1.1     -0.8
-  100		0.1    -0.2	0.7    -0.3
-   70   	         -0.6   -0.9    -0.7    -0.3
-   50   	         -1.5    -1.5    -1.4     -1.7

## Hurrell and Trenberth 1998

- MSU Version b

## Findings:

** ****Linear trends are bad!**
** ****Vertical structures are complex and cannot be resolved ****	****by broad layers**
** ****Temperature trends differ with level and time interval**
** ****Local and regional differences are large; **
**Global means are not useful: **
**for resolving processes or differences**
** ****Different processes are important at different levels**
**Surface: heat capacity;  land vs ocean**
**Stratosphere: ozone depletion**
**Troposphere: convection, subsidence, advection**
**Radiation: water vapor, cloud, aerosols, ozone, etc**

## 		Physical factors

**Stratospheric ozone depletion: **Cools MSU2
**Volcanic eruptions, episodic: ****	**Cools MSU2 more
**Greenhouse gases increasing:****	**Warms MSU2 more
**Aerosols (pollution) changing:****	**Complex; regional
**Solar variations:****	****	****	**Surface, stratosphere

**El Nino &**
**Other natural variability:**      Larger MSU2 response (60%)

**Day-night (max-min) T: **Affects surface more
**Land-ocean T contrasts: **
**	****	****	****	**Affects surface more
- 				Winds greater in troposphere

## QUESTIONS:

**Given that global mean surface temperature anomalies are dominated by continental land areas in the NH, while global “satellite temperature” anomalies are dominated by the Tropical regions, why should we expect a relationship at all?**
**How do the surface vs boundary layer vs troposphere temperatures covary regionally? **
**What are the differences and similarities regionally: **
** ****land vs ocean, tropics vs subtropics vs extratropics?**
**Why are there regions (e.g., the subtropics) where the surface and mid-troposphere monthly mean temperature anomalies are negatively ****	****correlated?**

## QUESTIONS:

**What are the characteristics of the trade wind inversion in terms of its ****	****level and intensity and how it varies, and how is that manifested in ****	****the satellite record and in models? **
**What are the characteristics of wintertime surface inversions over mid-****	****latitude continents (that provide a disconnect between the surface ****	****and the troposphere)?**
**What are the characteristics of the tropopause with annual cycle,  ENSO,****	****volcanoes,  and climate change?  Variations of 1 km in altitude can ****	****not be captured by the coarse resolution of the analysis or in models.**
**What can be said about the transition of warming near the surface to ****	****cooling in the stratosphere with climate change?**
**What is the diurnal cycle of temperature throughout the atmosphere and ****	****how does it alias onto satellite records that drift in local equator ****	****crossing time (LECT)?**
** ****Can we reconcile warmings found in tropical glaciers at about 500 to 600 ****	****mb with the tropospheric temperature record?**

## Is the vertical temperature profile different in regions with absorbing 	aerosols, and how much of that is because of no rain (allowing the 	aerosols to be present) vs the aerosol effects?

**What is the role of moisture and cloud changes?**
**What is the moisture budget in three dimensions and as a function of time?**
**What is the heat budget in three dimensions and as a function of time?**
**How are the atmospheric forcings changing?  How well are these known?**
**How and why are CO****2**** concentrations in the atmosphere changing?**
**How do changes in ozone amounts alter the vertical profile of ****	****temperatures?**
**How much net heat is going into the oceans and how much is being ****	****redistributed and released at different places and different times, ****	****such as during El Niño events?**
**Urban heat island effects are real climate changes but limited in areal ****	****extent.  How do they affect the temperature record?**
**Is the observational and analysis record adequate to address the above ****	****questions?**
**How well do climate models reproduce the local and global relationships ****	****between the surface and troposphere?**
**Can climate models be used for attribution of changes to forcings and ****	****processes?**