A comparison between CERES OLR and OLR calculated from AIRS - - PowerPoint PPT Presentation

▶
a comparison between ceres olr and olr calculated from
SMART_READER_LITE
LIVE PREVIEW

A comparison between CERES OLR and OLR calculated from AIRS - - PowerPoint PPT Presentation

Jan 09, 2023 253 likes •537 views

A comparison between CERES OLR and OLR calculated from AIRS temperature & humidity for clear-sky regions J. Lee, A. E. Dessler, P. Yang Department of Atmospheric Sciences Texas A&M University Water vapor (g/kg) 4 6 0.1 4 6 1 4 6 10 2

slide-1
SLIDE 1

A comparison between CERES OLR and OLR calculated from AIRS temperature & humidity for clear-sky regions

  • J. Lee, A. E. Dessler, P. Yang

Department of Atmospheric Sciences

Texas A&M University

slide-2
SLIDE 2

280 260 240 220 200 Temperature (K) 1000 1000 800 800 600 600 400 400 200 200 Pressure (hPa)

2 4 6 0.1 2 4 6 1 2 4 6 10

Water vapor (g/kg) Temperature Water vapor

2

slide-3
SLIDE 3

280 260 240 220 200 Temperature (K) 1000 1000 800 800 600 600 400 400 200 200 Pressure (hPa)

2 4 6 0.1 2 4 6 1 2 4 6 10

Water vapor (g/kg) Temperature Water vapor

Calculate OLR

3

slide-4
SLIDE 4

280 260 240 220 200 Temperature (K) 1000 1000 800 800 600 600 400 400 200 200 Pressure (hPa)

2 4 6 0.1 2 4 6 1 2 4 6 10

Water vapor (g/kg) Temperature Water vapor

Calculate OLR

4

Compare to CERES measurements

slide-5
SLIDE 5

Methodology

  • Use CERES Aqua SSF edition 2a data
  • Consider those CERES measurements

where > 96% of the collocated MODIS cloud-mask measurements are clear

  • Combine with AIRS measurements within

~20 km of the CERES measurement

  • Calculate TOA flux from CERES surface

skin temperature and AIRS profiles of q, T, and O3

  • Nighttime, ocean, March and September

2005

5

slide-6
SLIDE 6

Model

  • Chou et al., 2001: A Thermal Infrared Radiation Parameterization for

Atmospheric Studies. NASA Tech. Memo. 104606, vol. 19, 1-55.

  • The infrared spectrum (0~3000 cm-1) is divided into 9 bands and a

subband, in total 10 bands

  • Using the Air Force Geophysical Laboratory HITRAN data base (1996

version)

  • The parameterization includes the absorption due to major gaseous

absorption (water vapor, CO2, O3) and most of the minor trace gases (N2O, CH4, CFC’s) as well as clouds and aerosols.

  • The gaseous transmission function is computed either using the k-

distribution method or the table look-up method.

  • Accuracy: within 1% of the high spectral-resolution line-by-line calculation
  • In this calculation, band 9 (1900~3000 cm-1) is excluded to match with

CERES TOA flux band (50~2000 cm-1). The flux at 30 km between 1900 and 2000 cm-1 is 0.9 Wm-2 using tropical atmosphere.

  • Vertical atmospheric profiles from AIRS are used, including temperature,

water vapor, and ozone profile

  • Atmosphere is divided into 100 layers from surface to 100 km and the

AIRS profiles are interpolated at each level.

slide-7
SLIDE 7
  • Sept. 2005, 30°N-30°S
  • Avg. difference

4.7 W/m^2 Standard deviation 2.3 W/m^2 CERES=0.96 calc + 8

7

330 320 310 300 290 280 270 260 CERES OLR 330 320 310 300 290 280 270 260 Calculated OLR

slide-8
SLIDE 8

8

300 250 200 150 OLR (W/m^2) 10 8 6 4 2 Fraction of TNTC 188 K 194 K 191 K

Dessler et al. (2006), Tropopause-level thin cirrus coverage revealed by ICESat/ Geoscience Laser Altimeter System, J. Geophys. Res., 111, D08203, DOI: 10.1029/2005JD006586.

data at tropopause-level

slide-9
SLIDE 9
  • Sept. 2005, 30°N-30°S
  • Avg. difference

4.7 W/m^2 Standard deviation 2.3 W/m^2 CERES=0.96 calc + 8

9

330 320 310 300 290 280 270 260 CERES OLR 330 320 310 300 290 280 270 260 Calculated OLR

worse better

slide-10
SLIDE 10

10 300 298 296 294 292 290 288 286 OLR (W/m^2) 304 302 300 298 296 SST (K) ERBE RS+model ceres modelj ERBE analysis by Collins and Inamdar

  • J. Clim., 1995
slide-11
SLIDE 11

March 2005

  • 20
  • 10

10 20 360 270 180 90 300 290 280 270

Clear-sky OLR model - meas.

11

  • 20
  • 10

10 20 360 270 180 90 7 6 6 6 6 6 6 6 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 4 4 3

slide-12
SLIDE 12
  • Sept. 2005

Clear-sky OLR model - meas.

  • 20
  • 10

10 20 360 270 180 90 300 290 280 270 260

12

  • 20
  • 10

10 20 360 270 180 90 7 6 6 6 6 6 6 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 3

slide-13
SLIDE 13
  • Sept. 2005
  • Oct. 2003

Dessler, A.E., S.P. Palm, and J.D. Spinhirne (2006), Tropical cloud-top height distributions revealed by the Ice, Cloud, and Land Elevation Satellite (ICESat)/Geoscience Laser Altimeter System (GLAS), J. Geophys. Res., 111, D12215, DOI: 10.1029/2005JD006705. 13

  • 20
  • 10

10 20 360 270 180 90 7 6 6 6 6 6 6 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 3

slide-14
SLIDE 14

14 300 298 296 294 292 290 288 286 OLR (W/m^2) 302 300 298 296 SST (K) ceres modelj ERBE analysis by Collins and Inamdar

  • J. Clim., 1995

data from 9/05

slide-15
SLIDE 15

15 300 298 296 294 292 290 288 286 OLR (W/m^2) 302 300 298 296 SST (K) ceres modelj

data from 9/05

slide-16
SLIDE 16

16

Surface T 2.0 Lower Trop T 2.8 Upper Trop T 0.6 Lower Trop q

  • 7.9

Upper Trop q

  • 6.3

Compare to 299 to 303 K

303 K OLR 289.3 W/m^2 299 K OLR 297.7 W/m^2

∆OLR

  • 8.4 W/m^2

Lower Trop = 1000-500 hPa, Upper Trop = 500-100 hPa data from 9/05

slide-17
SLIDE 17

17 Correlation between the tropical averaged (20 N–20 S) daily temperature at 925 hPa and the tropical averaged daily temperature at other levels of the troposphere. AIRS data are represented by the black solid line, radiosonde by the black dashed line, and GCMs by the gray lines. 95% confidence intervals at 850 hPa, 500 hPa, and 200 hPa are plotted. Wu, Dessler, and North (2006), Analysis of the correlations between atmospheric boundary-layer and free- tropospheric temperatures in the Tropics, Geophys. Res. Lett., 33, L20707, DOI: 10.1029/2006GL026708.

slide-18
SLIDE 18

Variations of T with SST

18

data from 9/05

1000 800 600 400 200 Pressure (hPa) 302 300 298 296 Surface Temperature (K) 290 280 270 260 250 240 230

slide-19
SLIDE 19

Variations of q with SST

19

1000 800 600 400 200 Pressure (hPa) 302 300 298 296 Surface Temperature (K) 14 12 10 8 6 4 2 1 0.5 0.2 0.1

data from 9/05

slide-20
SLIDE 20

20 300 298 296 294 292 290 288 286 OLR (W/m^2) 302 300 298 296 SST (K) ceres modelj

data from 9/05

slide-21
SLIDE 21

21

Lower Trop = 1000-500 hPa, Upper Trop = 500-100 hPa

Compare to 295 to 299 K

299 K OLR 297.7 W/m^2 295 K OLR 285.3 W/m^2

∆OLR

12.4 W/m^2

299 K to: 295 K 303 K Surface T 8.3 2.0 Lower Trop T 9.7 2.8 Upper Trop T 4.8 0.6 Lower Trop q

  • 7.6
  • 7.9

Upper Trop q

  • 3.2
  • 6.3

data from 9/05

slide-22
SLIDE 22

Variations of q with SST

22

1000 800 600 400 200 Pressure (hPa) 302 300 298 296 Surface Temperature (K) 14 12 10 8 6 4 2 1 0.5 0.2 0.1

data from 9/05

slide-23
SLIDE 23

T’s effect on OLR

23

1000 800 600 400 200 304 302 300 298 296 294 Surface Temperature (K)

0.55 0.5 0.5 0.45 0.45 0.4 0.4 0.35 0.35 0.3 0.3 0.25 0.25 0.2 0.2 0.15 0.15 0.1 0.1 0.05

slide-24
SLIDE 24

q’s effect on OLR

24

1000 800 600 400 200 304 302 300 298 296 294 Surface Temperature (K)

0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.2 0.2 0.15 0.15 0.1 0.05

slide-25
SLIDE 25

25

250 200 150 100 50 % per (g/kg) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 H2O (g/kg) 346 hPa

Dessler and Minschwaner (2007), An analysis of the regulation of tropical tropospheric water vapor,

  • J. Geophys. Res., in press.
slide-26
SLIDE 26

26

Distance from detrainment (km) Dessler and Minschwaner (2007), An analysis of the regulation

  • f tropical tropospheric water vapor, J. Geophys. Res., in press.
slide-27
SLIDE 27

Conclusions

  • OLR calculated using AIRS measurements

agrees with CERES measurements within ~5 W/m^2

– Agreement best in the deep tropics and worst in the subtropics

  • We are also studying the mechanisms that

regulate clear-sky OLR

  • T and q are the most important factors

– T dominates below 298 K, q dominates above

27

This work was supported by a NASA EOS/IDS grant and by a NASA Aqua, Terra, ACRIM data analysis grant, both to Texas A&M