Showing papers by "Michael Jensen published in 2022"

The COMBLE campaign: a study of marine boundary-layer clouds in Arctic cold-air outbreaks

Abstract: One of the most intense air mass transformations on Earth happens when cold air flows from frozen surfaces to much warmer open water in cold-air outbreaks (CAOs), a process captured beautifully in satellite imagery. Despite the ubiquity of the CAO cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, its role in energy and water cycles, and its treatment in weather and climate models. The Cold-air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) was conducted to better understand this regime and its representation in models. COMBLE aimed to examine the relations between surface fluxes, boundary-layer structure, aerosol, cloud and precipitation properties, and mesoscale circulations in marine CAOs. Processes affecting these properties largely fall in a range of scales where boundary-layer processes, convection, and precipitation are tightly coupled, which makes accurate representation of the CAO cloud regime in numerical weather prediction and global climate models most challenging. COMBLE deployed an Atmospheric Radiation Measurement Mobile Facility at a coastal site in northern Scandinavia (69°N), with additional instruments on Bear Island (75°N), from December 2019 to May 2020. CAO conditions were experienced 19% (21%) of the time at the main site (on Bear Island). A comprehensive suite of continuous in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol were collected. Because of the clouds’ well-defined origin, their shallow depth, and the broad range of observed temperature and aerosol concentrations, the COMBLE dataset provides a powerful modeling test bed for improving the representation of mixed-phase cloud processes in large-eddy simulations and large-scale models.

Marine Boundary Layer Decoupling and the Stable Isotopic Composition of Water Vapor

Abstract: Decoupling of the subcloud layer in stratocumulus‐topped marine boundary layers (STMBL) influences low‐cloud cover by limiting the supply of water vapor from the surface. However, the relative importance of mixing between surface fluxes and other reservoirs of water vapor as a function of the degree of decoupling is poorly understood. Water vapor transport within the STMBL and its response to decoupling is explored using surface measurements of water vapor isotopic composition that were obtained from Graciosa Island, Azores, during the summer and fall of 2018. The data show an inverse relationship between the decoupling metric, Δq, and the degree of drying from an isotopically depleted water vapor source. The isotopic data require some degree of drying with an isotopically depleted source for coupled conditions, and likely require a small amount of mixing even for strongly decoupled conditions. The data are consistent with mixing between purely local reservoirs of water vapor, subjected to a small amount of condensation and fractionation, and do not require the invocation of large‐scale transport of water vapor aloft or additional cloud‐formation effects aloft.

A Succession of Cloud, Precipitation, Aerosol and Air Quality Field Experiments in the Coastal Urban Environment

Abstract: Within this context, fundamental questions regarding the life cycle of convective clouds, aerosols, and pollutants have brought together a diverse, integrated, and interagency collaboration of scientists to collect and analyze measurements, in the Houston, Texas, area, from the summer of 2021 through the summer of 2022, with subsequent modeling studies to address these important research objectives. The U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Facility and Atmospheric System Research (ASR) Program, the National Science Foundation’s (NSF’s) Physical and Dynamic Meteorology Program, the National Aeronautics and Space Administration’s (NASA’s) Tropospheric Composition Research and Health and Air Quality Applied Sciences Programs and the Texas Commission on Environmental Quality (TCEQ) are collaborating on a joint set of field campaigns to study the interactions of cloud, aerosol, and pollutants within the coastal, urban environment. Measurement platforms to be deployed: (a) Stony Brook University Weather Truck including dual-polarization X-band phased array radar (ESCAPE), (b) NCAR C-130 aircraft (ESCAPE) (photo credit: C. Wolff), (c) Pandora Spectrometer (TAQ) (photo credit: B. Swap), (d) ARM Tethered Balloon System (TRACER), (e) ARM Mobile Facility (TRACER), (f) C-Band ARM Scanning ARM Precipitation Radar (TRACER), (g) Baylor University–University of Houston–Rice University Mobile Air Quality Laboratory (TAQ, TRACER), (h) Johnson Space Flight Center Gulfstream V aircraft (TAQ). Measurement platforms to be deployed: (a) Stony Brook University Weather Truck including dual-polarization X-band phased array radar (ESCAPE), (b) NCAR C-130 aircraft (ESCAPE) (photo credit: C. Wolff), (c) Pandora Spectrometer (TAQ) (photo credit: B. Swap), (d) ARM Tethered Balloon System (TRACER), (e) ARM Mobile Facility (TRACER), (f) C-Band ARM Scanning ARM Precipitation Radar (TRACER), (g) Baylor University–University of Houston–Rice University Mobile Air Quality Laboratory (TAQ, TRACER), (h) Johnson Space Flight Center Gulfstream V aircraft (TAQ). Measurement platforms to be deployed: (a) Stony Brook University Weather Truck including dual-polarization X-band phased array radar (ESCAPE), (b) NCAR C-130 aircraft (ESCAPE) (photo credit: C. Wolff), (c) Pandora Spectrometer (TAQ) (photo credit: B. Swap), (d) ARM Tethered Balloon System (TRACER), (e) ARM Mobile Facility (TRACER), (f) C-Band ARM Scanning ARM Precipitation Radar (TRACER), (g) Baylor University–University of Houston–Rice University Mobile Air Quality Laboratory (TAQ, TRACER), (h) Johnson Space Flight Center Gulfstream V aircraft (TAQ). On the ground, multiple fixed and mobile radar systems (Fig. 1a) will be used to track convective cells and perform multi-Doppler analysis for the derivation of velocities within the convective systems over the course of their life cycle.

Linking Synoptic Patterns to Cloud Properties and Local Circulations Over Southeastern Texas

Abstract: This study classifies meteorological regimes in the southeastern Texas region to identify environmental conditions that favor sea‐breeze induced convection. The classification is accomplished using a Self‐Organizing Map (SOM) approach. We applied SOM to 10 years of 700‐hPa geopotential height anomalies during the summer months from reanalysis data to distinguish three dominant synoptic regimes, with a continuum of transitional states between those. The primary regimes include: (a) a pre‐trough regime associated with a synoptic trough, (b) a post‐trough regime with upper‐level northerly flow, and (c) an anticyclonic regime within the westward extent of the Bermuda High. We project the data from the Geostationary Operational Environmental Satellite and the Next Generation Weather Radar system onto each SOM node to investigate the characteristics of cloud and precipitation properties in different regimes. When southeastern Texas is positioned to the southwest quadrant of a maritime high pressure system, an increased cloud frequency is observed over the region during the afternoon hours due to significant moisture advection. A confluence of synoptic southerly flow and sea‐breeze circulation commonly occurs in this regime. When a high pressure system is over southeastern Texas, the area is dominated by large‐scale subsidence with weak pressure gradients and moderate precipitable water vapor. This weak synoptic forcing is favorable for the formation of a sea‐breeze circulation. This is confirmed by an enhanced onshore flow and a decreased temperature at the surface in the early afternoon, as well as a sharp increase in radar echo top height.

Convective Updraft and Downdraft Characteristics of Continental Mesoscale Convective Systems in the Model Gray Zone

Abstract: The “gray zone” of convective modeling is defined as the range of horizontal grid spacings (Δx) at which turbulent transport processes are only partially resolved by the dynamics of the numerical model. This zone typically covers Δx from a few kilometers to several hundred meters, wherein the realistic representation of convective cloud processes can be challenging. This study characterizes the convective draft behaviors at multiple Δx across the gray zone and determines the appropriate Δx that can reliably capture these salient convective properties. We perform an ensemble of idealized simulations of mesoscale convective systems (MCS) using the Weather Research and Forecasting model at various Δx from 4 km to 250 m over the central U.S. An evaluation of key MCS kinematic properties is constrained using unique, long‐term vertical velocity estimates obtained by radar wind profilers deployed by the Department of Energy Atmospheric Radiation Measurement user facility. MCS simulations for all Δx tested overestimate (underestimate) the probabilities of convective updrafts (downdrafts) compared to the observations. In terms of the convective draft intensity, finer‐Δx models overestimate the updraft intensity, while the opposite is found for downdrafts. Moving from Δx = 4 km to 250 m, downdrafts become stronger and more frequent especially at middle and upper levels, attributed to additional drag from an increasing graupel frequency and compensation of enhanced updraft velocity. Simulated draft characteristics, including core size, intensity, and probability of occurrence, exhibit pronounced changes at Δx greater than 500 m, but suggest less sensitivity when Δx is reduced below 500 m.

Convective Parameters Derived from Radiosonde Data (SONDEPARAM) Value-Added Product Report

Abstract: level, operating in maneuvers, or flying through cloud. Due to the nature of research flights, the payload of the aircraft consists of many duplicate and overlapping instruments to ensure, in case of instrument failure, there is a backup to record the data. Measurements from multiple instruments are consolidated into a single file. Each variable of this data set is carefully chosen from the onboard instrumentation and quality checked by AAF scientists to create this wholistic and most accurate data set for airborne research. This document is intended to be a hub towards the individual “read me” files produced for each campaign. For reference about what instrument was used for calculations on specific days, the read me files are located in the ARM IOP archive at the addresses listed, or access the IOP (intensive operational period) database at https://www.archive.arm.gov/.