Towards the Development of Global Scale Transferability of Inference Schemes for Radiative Forcing Functions under the CEOP Initiative

Department of Atmospheric and Oceanic Science
University of Maryland, College Park


Department of Atmospheric and Oceanic Science
 


Background

Approach

Parameters

Results
   
Available Data

References

Collaboration

Acknowledgements

Contacts

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Results

Selected Results

Indian Monsoon Region

The movement of Meteosat-5 over India starting in 1998 in support of the Indian Ocean Experiment (INDOEX) provides a unique opportunity to study in detail the daytime diurnal variability of clouds and components of the radiation budget over that region (Wonsick et al., 2009). Documented is the seasonal progression of the Asian monsoon as seen in clouds and convection in the pre-, peak-, and post-monsoon seasons. Diurnal variation of frequency of occurrence of low clouds (left column) and high clouds (right column) for pre-monsoon (Mar - May; top row), peak-monsoon (Jun - Sep; middle row), and post-monsoon (Oct - Nov; bottom row) seasons of 2001 for hours between 8 - 15 LST is shown in Figure 1; monthly mean cloud amount (%) is given in Figure 2; frequency of occurrence of convective clouds at selected daytime hours for the peak-monsoon season (Jun - Sep) 2001 is shown in Figure 3; cloud amount in % (top) and type (bottom) derived from Meteosat-5 for 1 Aug 04 at 07 UTC is shown in Figure 4; surface shortwave downward flux (W/m2) at 0.125° resolution from Meteosat-5 (top) and at 2.5° resolution from ISCCP D1 (bottom) is given in Figure 5.

The Tibetan Plateau

The Tibetan Plateau is the highest and biggest plateau of the world - "the roof of the world". The Plateau is interspersed with mountain ranges and its atmospheric environment has a great influence on the regional as well as global climate. Radiative fluxes play an important role in understanding the energy budget of this complex region and its hydrological cycle. Selected results will be illustrated. Instantaneous surface shortwave downward fluxes from Meteosat-5 for selected hours on July 1, 1998 at 0.125° resolution are shown in Figure 1; frequency of occurrence of convective clouds over the Tibetan Plateau at selected hours for the peak-monsoon season (Jun - Sep) 2001 is shown in Figure 2; comparison of monthly mean total cloud amount (%) at 06 UTC for each month of the 2001 monsoon season for Meteosat-5, ERA-40 Reanalysis, NCEP/NCAR Re-analysis, and ISCCP at 30° N and 82.5° E is shown in Figure 3.

The "Elevated Heat Pump" Hypothesis

It has been postulated that aerosol-induced anomalous mid-and upper-tropospheric warming above the Tibetan Plateau leads to an early onset and intensification of monsoon rainfall. This so-called "Elevated Heat Pump" effect is based on results from the NASA finite-volume general circulation model with and without radiative forcing from different types of aerosols (Lau et al., 2006)*.
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An observational approach to detect signatures of the "Elevated Heat Pump" effect in the cloud cover and cloud type distributions as derived from Meteosat-5 observations over the Asian Monsoon region, has been undertaken (Wonsick et al., 2009). The satellite data are supplemented with surface temperature data from the NCEP/NCAR Reanalysis and precipitation data from the Global Precipitation Climatology Project. Clouds, convection, precipitation, and surface temperature features for the highest-aerosol year of the current decade (2004) are compared with lower-aerosol content years during the period 2000 - 2005. Selected findings are illustrated here:

Evaluation of the EHP hypothesis: Selected findings
• Anomalous warming over the Tibetan Plateau was observed but appears too far north to be associated with the absorbing aerosols in the Indo-Gangetic Basin

• Enhanced convection in the foothills of the Himalayas and northward shift in precipitation in May was not observed

African Monsoon Region

Impact of Aerosols on Shortwave Flux Retrieval
The goal of the AMMA program is to improve understanding of the West African monsoon (WAM) and the factors that determine its variability on daily to inter-annual timescales. Radiative fluxes are needed for addressing the regional-scale processes of the WAM, where land-surface feedbacks are important. The AMMA region is frequented by dust outbreaks over Africa. It is important to incorporate the effects of dust on the radiative fluxes that reach the surface and control the hydrological cycle.

Global Scale

Methodologies have been dveloped to implement global scale spectral radiative flux schemes with MODIS 1 deg products. An example of monthly mean Photosynthetically Active Radiation for February 2003 is shown in Figure 1.

* Lau K-M, Kim MK, Kim KM (2006). Asian summer monsoon anomalies induced by aerosol direct forcing: the role of the Tibetan Plateau. Clim Dyn 26:855-864

Maintained by Chuan Li cli@atmos.umd.edu