Ceilometer observation of clouds during Indian summer monsoon: Relation with boundary layer and surface meteorology

Description

Monsoon is an economically important weather pattern in the Indian subcontinent and the most anticipated weather event. Yet it is only partially understood and notoriously difficult to predict. In order to understand this phenomenon at synoptic scale, it is essential to disseminate the cloud type and patterns at local scales during the season. Nainital is a high-altitude station (nearly 2 km above MSL), which often witnesses the pre-monsoon thunderstorms and rains basically driven by localized convective clouds. However, the contribution to the rains from monsoon clouds is more significant and can be better utilized to understand cloud microphysics.

To study the cloud-base height and hence indicating the cloud type (basically stratiform or boundary-layer clouds) a Vaisala ceilometer (VCEIL) installed at the ARM Mobile Facility (AMF1) site (ARIES), in Nainital as part of the GVAX field campaign has been operational since June 2011. VCEIL is a self-contained, ground-based, active remote sensing device designed to measure cloud-base height to a maximum of 7.6 km and potential backscatter signals by aerosols. It transmits near-infrared pulses of light (905 nm), and the receiver telescope detects the light scattered back by clouds and precipitation at every 15 m in the vertical. These measurements are used to produce derived products that are recorded, and the data archived during monsoon are analysed. The day-to-day first cloud base observed during the month of June 2011 ranges between 400 m to 3000 m, above ground level. In addition, the data obtained from the radar wind profiler and the collocated facilities for meteorological parameters are utilized to understand the lower atmospheric dynamics over the site of study. Details will be discussed during the poster presentation.