atmospheric hydrological cycle in the tropics in twentieth century coupled climate simulations
Download
Skip this Video
Download Presentation
Atmospheric Hydrological Cycle in the Tropics in Twentieth Century Coupled Climate Simulations

Loading in 2 Seconds...

play fullscreen
1 / 18

Atmospheric Hydrological Cycle in the Tropics in Twentieth Century Coupled Climate Simulations - PowerPoint PPT Presentation


  • 78 Views
  • Uploaded on

Atmospheric Hydrological Cycle in the Tropics in Twentieth Century Coupled Climate Simulations. Hailan Wang and William Lau Laboratory for Atmospheres, NASA/GSFC. Climate Model Evaluation Project (CMEP). 30 th Climate Diagnostics and Prediction Workshop October 26, 2005. Motivation.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Atmospheric Hydrological Cycle in the Tropics in Twentieth Century Coupled Climate Simulations' - evan-jimenez


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
atmospheric hydrological cycle in the tropics in twentieth century coupled climate simulations

Atmospheric Hydrological Cycle in the Tropics in Twentieth Century Coupled Climate Simulations

Hailan Wang and William Lau

Laboratory for Atmospheres, NASA/GSFC

Climate Model Evaluation Project (CMEP)

30th Climate Diagnostics and Prediction Workshop

October 26, 2005

motivation
Motivation
  • Identify and understand long-term change of tropical hydrological cycle in 20th Century climate simulations by Coupled GCMs
      • Precipitation
      • Clouds
  • Provide input for IPCC AR4 in 2007
slide3

Coupled GCMs

  • State-of-the-art
  • Fully coupled
    • Time signature differs
  • Driven by time-varying external climate forcings
    • No agreed-upon forcing functions
    • The diversity in external forcing in the CGCMs is regarded as a measure of forcing uncertainties
slide4

NASA GISS_E

http://www.giss.nasa.gov

/research/modeling/

slide5

Coupled GCMs (Cont’d)

  • 16 CGCMs analyzed
  • 1 run of each CGCM used
    • Monthly mean fields
    • 1900-1999
  • Linear trend (actual linear change over time period concerned)
    • Models: 1950-1999
    • Observations
      • 1979-1999 for GPCP precip
      • 1984-1999 for ISCCP clouds
slide6

USA: 5; France: 2; Japan: 2; UK: 2;

Australia: 1; Canada: 1; China:1; Germany: 1; Russia: 1

slide7

Linear Change of Surface Temp

Annual Mean 1950-1999

HadCRU (#17); NCEP CAMS (#18);

NOAA extended SST (#19)

slide8

Linear Change of Precip

Annual Mean 1979-1999

GPCP (#17)

slide9

Linear Trend of

Surface Temp (1950-99) and Precip (1979-99)

Obs

16 AR4 Model EnsMean

slide10

Distribution of GPCP Rain as a function of Rain Rate

Annual Mean 1979-1999; Tropical Ocean

Clim

Light: <1mm/day

Medium: 2-8mm/day

Heavy: >9mm/day

Trend

Rain Rate

slide11

Trend_Model*4

GFDL CM2.0

NASA GISS ER

MIROC3.2 hires

NCAR CCSM3

UKMO HadCM3

GPCP

slide12

Linear Change of Total Cloud Cover

Models (1950-1999) vs ISCCP/4 (1984-1999)

ISCCP (#17)

slide13

Clim and Linear Trend of 3-D Cloud in GFDL CM2.0

[1000mb-10mb]

[30S-30N]

[0-360E; 30S-30N]

slide14

Clim

Linear Trend

slide15

Linear Change over 1950-1999

500mb

Upward motion enhances

OLR at TOA

Chen et al (2002);

Wielicki et al (2002)

OLR reduces

slide16

OLR

Tropopause

Surface Evaporation

Cool Climate

Ocean surface

Tropical Ocean

OLR

Less OLR

Tropopause

More cold and bright high cloud at tropopause and lower stratosphere

Less high cloud

Intensified

deep convection

Strengthened

updraft

Less mid-to-low cloud

Increased

light rain

Enhanced

heavy rain

Greatly reduced

moderate rain

Enhanced Surface Evaporation

Warm Climate

Ocean surface

Warmer Tropical Ocean

conclusions
Conclusions
  • CGCMs are reasonably consistent in depicting aspects of long term changes in the 20th Century climate and the tropical hydrological cycle:
    • Surface warming over tropical ocean and land
    • Increasing/decreasing precipitation over tropical ocean/land
    • Increasing heavy and light rain, but decreasing moderate rain
    • A reduction in total cloud cover in the tropics.
  • CGCMs significantly underestimate the magnitudes of the observations, by a factor of at least 4.
    • This likely leads to gross errors in model simulation of tropical radiative fluxes
  • Difference between CGCMs and observations
    • Time scale
    • CGCMs: certain processes may be missing
    • Obs: e.g. problems in retrieving high level thin clouds
future
Future
  • Improvement in representing physical processes associated with clouds and their interaction with radiation in the CGCMs
  • Observational data
    • Quality
    • Long term
ad