Surface to atmosphere exchange has received much attention in numerical weather prediction models. This exchange is defined by turbulent parameters such as frictional velocity, drag coefficient and heat fluxes, which have to be derived experimentally from high-frequency observations. High-frequency measurements of wind speed, air temperature and water vapour mixing ratio (eddy covariance measurements), were made during the Integrated Ground Observation Campaign (IGOC) of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) at Mahabubnagar, India (16 • 44 N, 77 • 59 E) in the south-west monsoon season. Using these observations, an attempt was made to investigate the behaviour of the turbulent parameters, mentioned above, with respect to wind speed. We found that the surface layer stability derived from the Monin-Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds >4 m s −1 ; under stable regime for wind speeds <2 m s −1 and under neutral regime for wind speeds in the range of 2-3 m s −1 . All the three stability regimes were mixed for wind speeds 3-4 m s −1 . The drag coefficient shows scatter variation with wind speed in stable as well as unstable conditions.

Monsoon depressions, the main rain-producing systems over the Indian region along and near their tracks, are found to intensify the monsoon circulation by organizing low-level convergence. The normal track of the monsoon depressions is along the position of the monsoon trough at the surface, i.e., northwestward from the Head Bay of Bengal. Most of the monsoon depressions dissipate within one or two days after landfall. An unusual monsoon depression formed in the Bay of Bengal during the 1 st week of August 2006 causing heavy to very heavy rainfall over Madhya Pradesh, Maharashtra and Gujarat States of India. The track of this depression was anomalously southward from the mean track of the August depressions. It maintained its intensity during its longer travel. This paper addresses some of the dynamical characteristics of the depression in relation to its southward/westward track and longer travel. It is observed that horizontal advection of absolute vorticity above 550 hPa (below 600 hPa) along west (east) of the depression and maximum divergence of absolute vorticity below 400 hPa dominated for the westward movement of the depression. Increased moisture supply from the Arabian Sea (after the landfall of the depression) helped to maintain the intensity of the system throughout its long travel. The energy conversion terms revealed the strengthening of the zonal flow at higher levels prior to the formation of the depression.

This study is aimed at evaluating the impact of non-conventional winds using data obtained by INSAT

No abstract

No abstract