Grant Petty

and 1 more

Manual shipboard present weather reports from 1950 to 2019 are aggregated and composited yearly and seasonally on a $1^\circ \times 1^\circ$ grid to characterize the global climatology and long-term trends in the relative frequency of four categories of oceanic precipitation: drizzle, moderate and heavy non-drizzle, precipitation associated with thunderstorms and deep convection, and frozen-phase precipitation. Although ship reports are susceptible to subjective interpretation, the inferred distributions of these phenomena are consistent with datasets derived from other platforms. These distributions highlight widespread 70-year trends that are often consistent across both annual and seasonal frequencies, with statistical significance at 95\% confidence. The relative frequency of ship-reported drizzle has largely increased in the tropics annually and seasonally, with linear best-fit relative increases by as much as 15\% per decade. Decreased relative frequencies have been observed in parts of the subtropics and at higher latitudes. Heavier precipitation has encompassed a growing fraction of non-drizzle precipitation reports over the subtropical North Pacific and Mediterranean. The relative frequency of thunderstorm reports has declined over the open Atlantic but show positive trends over the Mediterranean and the western Atlantic. The trends in relative frozen precipitation occurrence suggest a poleward retreat of areas receiving frozen precipitation in the Northern Hemisphere. Possible mechanisms for these ship-observed trends are discussed and placed in the context of the modeled effects of climate change on global precipitation.

Brian J. Butterworth

and 44 more

The Chequamegon Heterogeneous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors 2019 (CHEESEHEAD19) is an ongoing National Science Foundation project based on an intensive field campaign that occurred from June-October 2019. The purpose of the study is to examine how the atmospheric boundary layer responds to spatial heterogeneity in surface energy fluxes. One of the main objectives is to test whether lack of energy balance closure measured by eddy covariance (EC) towers is related to mesoscale atmospheric processes. Finally, the project evaluates data-driven methods for scaling surface energy fluxes, with the aim to improve model-data comparison and integration. To address these questions, an extensive suite of ground, tower, profiling, and airborne instrumentation was deployed over a 10×10 km domain of a heterogeneous forest ecosystem in the Chequamegon-Nicolet National Forest in northern Wisconsin USA, centered on the existing Park Falls 447-m tower that anchors an Ameriflux/NOAA supersite (US-PFa / WLEF). The project deployed one of the world’s highest-density networks of above-canopy EC measurements of surface energy fluxes. This tower EC network was coupled with spatial measurements of EC fluxes from aircraft, maps of leaf and canopy properties derived from airborne spectroscopy, ground-based measurements of plant productivity, phenology, and physiology, and atmospheric profiles of wind, water vapor, and temperature using radar, sodar, lidar, microwave radiometers, infrared interferometers, and radiosondes. These observations are being used with large eddy simulation and scaling experiments to better understand sub-mesoscale processes and improve formulations of sub-grid scale processes in numerical weather and climate models.