Spatial and Temporal Distribution of Latent Heating in the South Asian Monsoon Region

Abstract

Information from the Tropical Rainfall Measuring Mission (TRMM) level 3 monthly 0.58 3 0.58 Convective and Stratiform Heating (CSH) product and TRMM Microwave Imager (TMI) 2A12 datasets is used to examine the four-dimensional latent heating (LH) structure over the Asian monsoon region between 1998 and 2006. High sea surface temperatures, ocean-land contrasts, and complex terrain produce large precipitation and atmospheric heating rates whose spatial and temporal characteristics are relatively undocumented. Analyses show interannual and intraseasonal LH variations with a large fraction of the interannual variability induced by internal intraseasonal variability. Also, the analyses identify a spatial dipole of LH anomalies between the equatorial Indian Ocean and the Bay of Bengal regions occurring during the summer active and suppressed phases of the monsoon intraseasonal oscillation. Comparisons made between the TRMM CSH and TMI 2A12 datasets indicate differences in the shape of the vertical profile of LH. A comparison of TRMM LH retrievals with sounding budget observations made during the South China Sea Monsoon Experiment shows a high correspondence in the timing of positive LH episodes during the rainy periods. Negative values of atmospheric heating, associated with radiative cooling and with upper-tropospheric cooling from nonsurfaceprecipitating clouds, are not captured by either of the TRMM datasets. In summary, LH algorithms based on satellite information are capable of representing the spatial and temporal characteristics of the vertically integrated heating in the Asian monsoon region. However, the vertical distribution of atmospheric heating is not captured accurately throughout different convective phases. It is suggested that satellite-derived radiative heating/cooling products are needed to supplement the LH products in order to give a better overall depiction of atmospheric heating.

Estimating Vertical Motion Profile Shape within Tropical Weather States over the Oceans

“…These algorithms consider surface precipitation, percent stratiform rain fraction, and, for the PRH product, vertical profiles of reflectivity. Along with this, several other studies (Zuluaga et al 2010;Jiang et al 2011;Ling and Zhang 2011) suggest that shallow heating is particularly difficult to retrieve. 3 in their study).…”

Characteristics of a persistent "pool of inhibited cloudiness" and its genesis over the Bay of Bengal associated with the Asian summer monsoon

“…The largest monthly mean values of LH over the above deep convective regions (though having considerable spatio-temporal variations) occur between 3-7 km altitude where it is typically in the range of 1.4 to 4.0 K day −1 , while the corresponding values of LH over the "pool" are negligible (Zuluaga et al, 2010). Whereas the synoptic-scale monsoon circulation provides the main closure mechanism for the updraft at the fixed zones of deep convection, this study shows that the mini-circulation described above also contributes significantly to the maintenance of large-scale convection at the above zones and hence would be an important component of the ASM.…”

“…Distribution of clouds over the Indian subcontinent and the surrounding regions during ASM (JuneSeptember period) has several important features. For example, the highest cloud top altitudes and integrated latent heat release (Zuluaga et al, 2010) over the planet occur over the Bay of Bengal (BoB) during ASM. In contrast to the near-cancellation of the longwave and shortwave cloud radiative forcing at the top-of-atmosphere over the tropics, net cloud radiative forcing over a vast region in the Indian subcontinent and the surrounding oceans is negative during ASM (Rajeevan and Srinivasan, 2000;Roca et al, 2005).…”

Investigation of negative cloud radiative forcing over the Indian subcontinent and adjacent oceans during the summer monsoon season

“…Long-term studies show that the northern Bay of Bengal region during the summer monsoon season is characterized by a large amounts of high clouds with cloud-top altitude close to the tropical tropopause (Devasthale and Fueglistaler, 2010;Meenu et al, 2010). The region also experiences the highest integrated latent heat release observed over the planet during the Asian summer monsoon season (Zuluaga et al, 2010). Rajeevan and Srinivasan (2000) proposed that the presence of large amounts of optically thicker high-level clouds are the main reason behind the observed negative NETCRF over the Bay of Bengal.…”