Climatology and Detection of Overshooting Convection From 4 Years of GPM Precipitation Radar and Passive Microwave Observations

Abstract

A 4-year Global Precipitation Measurement (GPM) Precipitation Feature (PF) data set is used to quantify the frequency and global distribution of overshooting convection. In this study, overshooting convection is defined as PFs with maximum 20 dBZ echo top height (MAXHT20) greater than the height of the lapse rate tropopause, derived from ERA-Interim reanalysis data. The geographical distribution of overshooting convection exhibits a strong preference for specific land regions, such as over the central United States, Argentina, Central Africa, and Colombia. Larger areas and greater occurrence of 20 dBZ radar reflectivity at the tropopause are found in northern middle to high latitudes than in the tropics. The occurrence of 20 dBZ radar reflectivity reaching above the level of 380 K potential temperature (Z 380K ) in middle and high latitudes is found to be comparable to that in the tropics. Furthermore, a methodology is developed to detect overshooting convection using the GPM Microwave Imager measured brightness temperature at 183.31 ± 3 and 183.31 ± 7 GHz, and Polarization Corrected Temperature at 89 GHz. The geographical distribution of overshooting convection can be closely reproduced using the combinations of these brightness temperatures with an average Heidke skill score of 0.4 and probability of 0.38. This shows the possibility of identifying overshooting convection from microwave observations at high-frequency channels near the water vapor absorption line centered at 183.31 GHz from other satellite missions.

A 13‐year Trajectory‐Based Analysis of Convection‐Driven Changes in Upper Troposphere Lower Stratosphere Composition Over the United States

“…Finally, because our trajectory calculations are initialized in and outside of convection only within the CONUS and the history of the tracked air masses prior to their transit across the CONUS is unknown, it is possible that convective influence is substantially underestimated due to echo‐free trajectories having recent convective origins outside of the CONUS and longer‐term association with convection than that captured by our trajectories (e.g., hydration 10 days prior rather than 3 days prior). Such convective contamination of our echo‐free population would be most likely during late summer, when deep (and often, tropopause‐overshooting) convection has been occurring for long periods of time and can be found frequently nearby over the Sierra Madre Occidental of Mexico and in south‐central Canada (e.g., N. Liu et al., 2020). Deep convection over the Sierra Madre is most frequent, but transit times of influenced air to the CONUS are often slow due to long paths followed initially west, then north and east through the North American upper troposphere monsoon anticyclone.…”

A 22‐Year Evaluation of Convection Reaching the Stratosphere Over the United States

“…Some general results of these studies are: (a) LRT overshooting is most frequent over land, (b) overshooting occurs primarily during the warm season, and (c) the deepest and most frequent regions of LRT overshooting are found in the midlatitudes. The contiguous United States (CONUS) is one of the most active regions for LRT overshooting found anywhere around the globe (e.g., N. Liu & Liu, 2016; N. Liu et al., 2020). The CONUS has been the focus of several recent long‐term studies of LRT overshooting using gridded observations from the operational ground‐based radar network (the GridRad data set, which is used here).…”

“…the most active regions for LRT overshooting found anywhere around the globe (e.g., N. Liu & Liu, 2016;N. Liu et al, 2020).…”

Comparing Tropopause‐Penetrating Convection Identifications Derived From NEXRAD and GOES Over the Contiguous United States

“…Updrafts that elevate cloud tops above the tropopause are common within deep convective storms over the contiguous US (CONUS), with tens of thousands of these overshooting tops (OTs) occurring in a given year (Bedka et al., 2010; Cooney et al., 2018; Liu & Zipser, 2005; Liu et al., 2020; Solomon et al., 2016). OTs in the mid‐latitudes are closely connected to the seasonal evolution of convection and the tropopause and thus, most frequently occur during the early summer months when the tropopause altitude is lower than later summer months and convective activity is higher than during the winter (Cooney et al., 2018; Dai et al., 1999; Solomon et al., 2016).…”

“…Its successor, the Global Precipitation Measurement Mission (GPM) (Hou et al., 2014), collected passive microwave imager data with higher spatial detail and multi‐frequency radar profiles extending to a 65° latitude, compared to the ∼35° latitude extent observed by TRMM. Precipitation echo tops at low reflectivity thresholds, such as a range between 5 and 20 dBZ, are a proxy for cloud top height that can be compared with various reference levels such as the equilibrium level (commonly referred to as the level of neutral buoyancy), the tropopause altitude, or the 380 K isentrope to identify OTs (Liu & Zipser, 2005; Liu et al., 2020). Convective updrafts with large ice particles or high concentrations of ice scatter microwave radiation before it reaches the satellite sensor, generating prominent brightness temperature depressions (Bang & Cecil, 2019) that have been used to infer the presence of OTs (Liu et al., 2020).…”