Planetary boundary layer height by means of lidar and numerical simulations over New Delhi, India

Abstract

Abstract. In this work, the height of the planetary boundary layer (PBLH) is investigated over Gwal Pahari (Gual Pahari), New Delhi, for almost a year. To this end, ground-based measurements from a multiwavelength Raman lidar were used. The modified wavelet covariance transform (WCT) method was utilized for PBLH retrievals. Results were compared to data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and the Weather Research and Forecasting (WRF) model. In order to examine the difficulties of PBLH detection from lidar, we analyzed three cases of PBLH diurnal evolution under different meteorological and aerosol load conditions. In the presence of multiple aerosol layers, the employed algorithm exhibited high efficiency (r=0.9) in the attribution of PBLH, whereas weak aerosol gradients induced high variability in the PBLH. A sensitivity analysis corroborated the stability of the utilized methodology. The comparison with CALIPSO observations yielded satisfying results (r=0.8), with CALIPSO slightly overestimating the PBLH. Due to the relatively warmer and drier winter and, correspondingly, colder and rainier pre-monsoon season, the seasonal PBLH cycle during the measurement period was slightly weaker than the cycle expected from long-term climate records.

Seasonal analysis of submicron aerosol in Old Delhi using high resolution aerosol mass spectrometry: Chemical characterisation, source apportionment and new marker identification

“…These observations are supported by laboratory studies which show atmospheric ammonia and alkanoic acids react to form alkyl cyanides via an amide intermediate (Simoneit et al, 2003;Zhao et al, 2009). The characteristically high ammonia concentrations in Delhi could therefore make this a viable reaction pathway (Saraswati et al, 2018;Nakoudi et al, 2019). 625…”

“…This was mainly due to the contraction of the boundary layer during the night and early hours of the morning being more pronounced which removes possible afternoon peaks 240 from specific sources, e.g. lunch hour cooking activities (Nakoudi et al, 2019;Reyes-Villegas et al, 2020). The pre-monsoon and monsoon diurnal cycles show species concentrations, excluding nitrate and chloride, were less affected by the higher boundary layer in the afternoon.…”

Variability of the Boundary Layer Over an Urban Continental Site Based on 10 Years of Active Remote Sensing Observations in Warsaw

“…Each of these approaches has its limitations regarding the measurement range and accuracy, spatial and temporal resolution, and weather conditions (clouds, fog, and precipitation). The ABLH measurement range and accuracy issues were solved to a large extent with the development of the light detection and ranging technology, e.g., by using next-generation high-power lidars [25][26][27] or low-power lidars and ceilometers [28][29][30][31]. The latter are recognized worldwide as efficient and affordable ground-based instruments for profiling of the atmosphere [32].…”

“…The determination of ABLH from ceilometer and lidar is based on using the elastic backscatter signals, whereby the ABLH is derived by relying on a higher aerosol load within the boundary layer than in the free troposphere. Several algorithms based on the aerosol load difference have emerged, to name just a few: The first or second derivative methods [35,36], logarithm gradient of the backscatter signal method [22,29,37], backscatter threshold determination [29,38], temporal analysis of the return signal of the standard deviation or variance [39], idealized backscatter fitting [40], and wavelet covariance transform [25,27,41]. In some approaches, a combination of those is applied [12,[42][43][44][45].…”

“…Most of the studies reported in the literature focus on ABLH retrieval during the daytime and for fair-weather conditions [24,28,34,[37][38][39][40] while retrievals during complex weather situations, as well as during the sunrise/sunset and at nighttime, have been performed less often [27,29,31,46]. The most complex boundary layer and aerosol conditions often form at night, which is regarded as an important part of the diurnal changes within the ABL, and thus the nocturnal boundary layer should not be excluded from the ABLH statistical analysis.…”