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Global constraints on momentum and energy govern the variability of the rainfall belt in the intertropical convergence zone and the structure of the zonal mean tropical circulation. The continental-scale monsoon systems are also facets of a momentum- and energy-constrained global circulation, but their modern and palaeo variability deviates substantially from that of the intertropical convergence zone. The mechanisms underlying deviations from expectations based on the longitudinal mean budgets are neither fully understood nor simulated accurately. We argue that a framework grounded in global constraints on energy and momentum yet encompassing the complexities of monsoon dynamics is needed to identify the causes of the mismatch between theory, models and observations, and ultimately to improve regional climate projections. In a first step towards this goal, disparate regional processes must be distilled into gross measures of energy flow in and out of continents and between the surface and the tropopause, so that monsoon dynamics may be coherently diagnosed across modern and palaeo observations and across idealized and comprehensive simulations. Accounting for zonal asymmetries in the circulation, land/ocean differences in surface fluxes, and the character of convective systems, such a monsoon framework would integrate our understanding at all relevant scales: from the fine details of how moisture and energy are lifted in the updrafts of thunderclouds, up to the global circulations.

Lightning is an important atmospheric process for generating reactive nitrogen, resulting in the production of tropospheric ozone, as well as igniting wildland fires, which result in potentially large emissions of many pollutants and short-lived climate forcers. Lightning is also expected to change in frequency and location with the changing climate. As such, lightning is an important component of Earth system models. Until now, the Canadian Earth System Model (CanESM) did not contain an interactive-lightning parameterization. The fire parameterization in CanESM5.1 was designed to use prescribed monthly climatological lightning. In this study, we have added a logistical regression lightning model that predicts lightning occurrence interactively based on three environmental variables and their interactions in CanESM5.1's atmospheric model, CanAM5.1 (Canadian Atmospheric Model), creating the capacity to interactively model lightning, allowing for future projections under different climate scenarios. The modelled lightning and resulting burned area were evaluated against satellite measurements over the historical period, and model biases were found to be acceptable. Modelled lightning had a small negative bias and excellent land–ocean ratio compared to satellite measurements. The modified version of CanESM5.1 was used to simulate two future climate scenarios (SSP2-4.5 and SSP5-8.5; Shared Socioeconomic Pathway) to assess how lightning and burned area change in the future. Under the higher-emissions scenario (SSP5-8.5), CanESM5.1 predicts almost no change to the global mean lightning flash rate by the end of the century (2081–2100 vs. 2015–2035 average). However, there are substantial regional changes to lightning – particularly over land – such as a mean increase of 6 % in the northern mid-latitudes and decrease of -8 % in the tropics. By the century's end, the change in global total burned area with prescribed climatological lightning was about 2 times greater than that with interactive lightning (42 % vs. 26 % increase, respectively). Conversely, in the northern mid-latitudes the use of interactive lightning resulted in 3 times more burned area compared to that with unchanging lightning (48 % vs. 16 % increase, respectively). These results show that the future changes to burned area are greatly dependent on a model's lightning scheme, both spatially and overall. [ABSTRACT FROM AUTHOR]

The Student Operational Aggie Doppler Radar Project (SOAP) involved 95 undergraduates in a research and education program to better understand the climatology of storms in southeast Texas from 2006-2010. This paper describes the structure, components, and implementation of the 1-credit-hour research course, comparing first-year participants' experiences and career outcomes with students who were engaged in SOAP for multiple years. Groups of five or six students, led by a senior-level undergraduate and mentored by a graduate student and faculty advisor, performed several daily research tasks, including producing precipitation forecasts, archiving observations, and operating and analyzing data from an S-band Doppler radar for precipitation events on their assigned day. Anonymous surveys given to SOAP students at the end of each semester indicated that student confidence in performing most SOAP tasks exhibited statistically significant positive correlations with their interest and experience in doing them. In addition, students participating in SOAP for multiple years were significantly more confident in performing program tasks than single-year participants (with correlations increasing an average of 19%) and were more likely to obtain meteorology or science-related employment upon graduation (94% versus 69%). First-year participants were significantly more likely to indicate that their interactions with undergraduate student leaders or peers were most beneficial, whereas interactions with the faculty advisor or graduate student mentors were equally or more important to returning students. Students were also more likely to consider research careers and matriculate to graduate programs as they participated longer in SOAP, suggesting research and education programs have a strong influence on students' career outcomes in addition to fostering positive self-efficacy.

Lightning is an important atmospheric process for generating reactive nitrogen, resulting in production of tropospheric ozone, as well as igniting wildland fires, which result in potentially large emissions of many pollutants and short-lived climate forcers. Lightning is also expected to change in frequency and location with the changing climate. As such, lightning is an important component of Earth system models. Until now, the Canadian Earth System Model (CanESM) did not contain an interactive lightning parameterization. The fire parameterization in CanESM5.1 was designed to use prescribed monthly climatological lightning. In this study, we have added a logistical regression lightning model that predicts lightning occurrence interactively based on three environmental variables and their interactions into CanESM5.1's atmospheric model, CanAM5.1, creating the capacity to interactively model lightning, allowing for future projections under different climate scenarios. The modelled lightning and resulting burned area were evaluated against satellite measurements over the historical period and model biases were found to be acceptable. Modelled lightning was within a factor of two of the measurements and had exceptionally accurate land/ocean ratios. The modified version of CanESM5.1 was used to simulate two future climate scenarios (SSP2-4.5 and SSP5-8.5) to assess how lightning and burned area change in the future. Under the higher emission scenario (SSP5-8.5), CanESM5.1 predicts an increase in northern mid-latitude lightning flashrate of 5%, but a decrease in tropical lightning of -10%, resulting in almost no change to the global mean lightning amount by the end-of-the century (2081-2100 vs 2015-2035 average). By century's end, the change in global total burned area with prescribed climatological lightning was about two times greater than that with interactive lightning (43% vs 19% increase, respectively). Conversely, in the northern mid-latitudes the use of interactive lightning resulted in three times more area burned as that with unchanging lightning (36% vs 13% increase, respectively). These results show that the future changes to burned area are greatly dependent on a model's lightning scheme, both spatially and overall. [ABSTRACT FROM AUTHOR]

Diurnal variations in the shallow and deep meridional overturning over West Africa during the premonsoon (April–May) and monsoon (July–September) seasons were analyzed using ECMWF Reanalysis 5th Generation (ERA5) reanalysis and Tropical Rainfall Measuring Mission (TRMM)/Global Precipitation Measurement (GPM) satellite radar data from 1998 to 2019. We found that a daytime sea breeze and two nocturnal low‐level jets have varying impacts on the diurnal cycle of convection and the meridional circulations over West Africa, depending on the season. During the premonsoon, the zonal rain belt is centered over the Gulf of Guinea and the sea breeze initiates intense deep convection (and thus deep overturning) over the coastal region in the afternoon that propagates northward into the early evening. The nocturnal Sahel/Sahara low‐level jet (SLLJ) then drives low‐level convergence into the West African heat low, producing a strong, dry shallow overturning over land at night. During the monsoon, the rain belt is centered over land (10∘$$ 1{0}^{\circ } $$N) and the sea breeze is forced by weaker temperature gradients, producing less intense convection that does not propagate as far inland as during the premonsoon. However, organized convection inland maintains deep daytime overturning. At night, a coastal low‐level jet strengthens northward moisture transport from the Gulf of Guinea into the active monsoon region after the sea breeze dissipates, helping maintain convective systems with large stratiform components and continued deep meridional overturning over land. The nocturnal SLLJ still drives low‐level convergence into the West African heat low, but the dry shallow meridional overturning is farther north and weaker than in the premonsoon. While ERA5 winds and moisture‐flux convergence are generally consistent with diurnal variations in the TRMM/GPM precipitation, ERA5 precipitation is not. The reanalysis indicates significant biases in the timing and magnitude of rainfall over the Gulf of Guinea and West Africa in each season, with the convective and large‐scale rain fields both contributing to the disparate precipitation patterns. [ABSTRACT FROM AUTHOR]

Heating profiles calculated from sounding networks and other observations during three Tropical Rainfall Measuring Mission (TRMM) field campaigns [the Kwajalein Experiment (KWAJEX), TRMM Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), and South China Sea Monsoon Experiment (SCSMEX)] show distinct geographical differences between oceanic, continental, and monsoon regimes. Differing cloud types (both precipitating and nonprecipitating) play an important role in determining the total diabatic heating profile. Variations in the vertical structure of the apparent heat source, [Q.sub.1], can be related to the diurnal cycle, large-scale forcings such as atmospheric waves, and rain thresholds at each location. For example, TRMM-LBA, which occurred in the Brazilian Amazon, had mostly deep convection during the day while KWAJEX, which occurred in the western portion of the Pacific intertropical convergence zone, had more shallow and moderately deep daytime convection. Therefore, the afternoon height of maximum heating was more bottom heavy (i.e., heating below 600 hPa) during KWAJEX compared to TRMM-LBA. More organized convective systems with extensive stratiform rain areas and upper-level cloud decks tended to occur in the early and late morning hours during TRMM-LBA and KWAJEX, respectively, thereby causing [Q.sub.1] profiles to be top heavy (i.e., maxima from 600 to 400 hPa) at those times. SCSMEX, which occurred in the South China Sea during the monsoon season, had top-heavy daytime and nighttime heating profiles suggesting that mesoscale convective systems occurred throughout the diurnal cycle, although more precipitation and upper-level cloud in the afternoon caused the daytime heating maximum to be larger. A tendency toward bottom- and top-heavy heating profile variations is also associated with the different cloud types that occurred before and after the passage of easterly wave troughs during KWAJEX, the easterly and westerly regimes during TRMM-LBA, and the monsoon onset and postonset active periods during SCSMEX. Rain thresholds based on heavy, moderate, and light/no-rain amounts can further differentiate top-heavy heating, bottom-heavy heating, and tropospheric cooling. These budget studies suggest that model calculations and satellite retrievals of [Q.sub.1] must account for a large number of factors in order to accurately determine the vertical structure of diabatic heating associated with tropical cloud systems.