Convective mixing, PBL heights and diurnal variability of Aerosols during GVAX

Description

V. Rao Kotamarthi, D V Phanikumar, Manish Naja and Yan Feng Strong diurnal variability in absorbing aerosols has been observed at Nainital, India during the Ganges Valley Aerosol Experiment (June 2011-March 2012). The diurnal variability has been associated with the changes in PBL mixing height that brings aerosols from the polluted lower valley region to the more pristine elevated site at Nainital, located 2 km above MSL. Here, we explore the measured variability of aerosols and its correlation with increased convective activity and PBL height variability measured at Nainital using a high resolution model (WRF) and observations of aerosol properties by using Doppler Lidar, MPL and AOS instrumentation. The vertical velocities observed in stable boundary layer are observed to be ~ 30-40 cm/s, however, convective boundary layer shows vertical velocities of the order of ~ 3-4 m/s. Moreover, Range Height Indicator (RHI) and Plane Position Indicator (PPI) scan modes provide information about the vertical transport from nearby valley regions. Diurnal variation of boundary layer shows the boundary layer height of ~ 0.6-0.8 km and nighttime it is considerably lower at less than ~ 0.3-0.4 km based on DL measurements. We will explore the drivers of vertical and temporal variability using model simulations and provide estimates of expected transport of aerosols from the surface to the cleaner higher altitudes over this region. It is likely that this is an additional mechanism that transports absorbing aerosols over the Himalayas and its glaciers. We will provide estimates of the potential source strength.