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Regional variation of electrical and lightning properties of thunderclouds is investigated by using simultaneous observations of electric field mill (EFM-100) and lightning detector (LD-350) in synergy with their radiance and bulk microphysical properties. The study is carried out over Kohima in the north-eastern and over Rampurhat in the eastern part of India (20o-30o N, 85o-96o E), during the pre-monsoon season (March–May) of 2017–2018. The occurrence of EFM-100 detected thunderclouds is found to be more over Kohima (111) compared to Rampurhat (88). Whereas, the average number of lightning flash is much higher over Rampurhat (~542 flash/thundercloud) compared to Kohima (~32 flash/thundercloud). Over both the regions, the maximum occurrence of thunderclouds is found during afternoon to evening hours. The upper whisker value in the box plot shows that thunderclouds over Rampurhat are associated with higher CAPE value (Kohima: 1100 J Kg−1; Rampurhat: 5000 J Kg−1). The diurnal variation of CAPE supports relatively early occurrence of thunderclouds over Kohima. Thunderclouds over Rampurhat persists for relatively longer duration. It is observed that overall percentage occurrence of CG lightning is more over Kohima (Kohima: −CG: 28.09% & +CG: 09.74%; Rampurhat (–CG: 12.33% & +CG: 08.60%), with relatively higher −CG lightning compared to +CG, over both the stations. On the contrary, the occurrence of IC lightning is more over Rampurhat (Rampurhat: −IC: 31.75% & +IC: 47.30%; Kohima: −IC: 36.44% & +IC: 25.72%). Over Kohima occurrence of −IC is more than the +IC, whereas over Rampurhat, the occurrence of +IC is more than −IC. The overall higher occurrence of total negative and positive discharges over Kohima and Rampurhat respectively is consistence with EFM observations. The prevalence of positive/negative discharge suggests the presence of a tripole charge structure within thunderclouds over both the regions. The upper whisker value in the box plots revels higher CG flash density, IC:CG and larger log(area) over Rampurhat (Kohima: 3.0 × 10−3 flash km−2 h−1 and Rampurhat: 4.25 × 10−3 flash km−2 h−1; Kohima: 7 and Rampurhat: 15; Kohima: 10.5 km2 and Rampurhat: 11.5 km2). The lower whisker value of cloud top temperature reveals prevalence of colder thunderclouds over Rampurhat (Kohima: 220 K; Rampurhat: 184 K). The thunderclouds over Rampurhat are found to be associated with stronger updrafts and mixed-phase processes. The study reveals that, over these two regions, the electrical and lightning properties have distinct characteristics.

A temperature inversion layer often occurs above a cloud layer due to longwave cooling in the upper cloud levels; however, few previous studies have been conducted on the climatologic statistics of cloud-top temperature inversion features. By using a high-quality continuous radiosonde dataset from 2002/05 to 2014/05 at the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) site at the islands of Manus and North Slope of Alaska (NSA) site near Barrow, Alaska, this study investigated the long-term characteristics of cloud-top temperature inversion over the single- and double-layer clouds (SLC and DLC, respectively) in these two different geographic locations and climate regimes. Cloud tops extended much higher vertically at the TWP than at the NSA due to their different local atmospheric environments. Because of the radiative energy interactions between the two layers of clouds, a thinner temperature inversion depth was presented by the DLC lower clouds than by the DLC higher clouds at the TWP site. However, much weaker temperature inversions were detected above the DLC higher clouds than the DLC lower clouds which were often bounded by a ubiquitous surface radiative cooling-induced inversion at the NSA site. A close temperature inversion was observed between the morning and evening at both sites. A thinner temperature inversion depth was displayed in the summer and autumn melt seasons when weak surface radiative cooling occurred at the NSA, whereas a smooth seasonal temperature inversion occurred at the TWP. The climatologic results of this study are expected to provide a better understanding of the complex interactions between clouds and temperature inversion, especially their unique climatic features in the tropics and Arctic.

Using the Himawari-8 cloud product, this study investigated the seasonal, monthly, diurnal variations as well as spatial and vertical distributions of cloud properties over four typical regions, which are northwest (NW), north (N), southeast (SE) China and Tibetan Plateau (TP). The results show that the cloud occurs most frequently in spring and summer, and the seasonal average cloud top height (CTH) has clear seasonal differences while the cloud top temperature (CTT) is negatively correlated with CTH. A unimodal structure is found for the vertical distribution of occurrence frequency of CTH over SE and TP. By dividing clouds into four types, they show large differences in the probability of occurrence. The study also shows that the monthly cloud fraction (CF) is larger in summer and less in winter except in SE, the monthly CTH changes are relatively small in SE and TP, while the monthly CTT variation is the largest in TP. The total CF increases by 22%, 8%, 3%, and 16% from morning to afternoon in four study areas, respectively. The proportion of four types of cloud families has weak diurnal variation except over TP. In TP, the proportions of high cloud (HC) and low cloud (LC) have a diurnal variation of 30% and 22%, respectively. Note that the relative CF contribution (RCFC) of LC reaches the maximum values in the morning. With the enhancement of convection, the RCFC of DCC and HC increases rapidly. Associated with more active convections, the diurnal variations of CTH and CTT are larger in TP than those in other regions. The clouds in SE have a larger COT and smaller CTH than in other regions, implying more sufficient water supply with low clouds.