Kristopher M. Bedka

Increase in upper tropospheric and lower stratospheric aerosol levels and its potential connection with Asian pollution

Satellite observations have shown that the Asian Summer Monsoon strongly influences the upper troposphere and lower stratosphere (UTLS) aerosol morphology through its role in the formation of the Asian Tropopause Aerosol Layer (ATAL). Stratospheric Aerosol and Gas Experiment II solar occultation and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar observations show that summertime UTLS Aerosol Optical Depth (AOD) between 13 and 18 km over Asia has increased by three times since the late 1990s. Here we present the first in situ balloon measurements of aerosol backscatter in the UTLS from Western China, which confirm high aerosol levels observed by CALIPSO since 2006. Aircraft in situ measurements suggest that aerosols at lower altitudes of the ATAL are largely composed of carbonaceous and sulfate materials (carbon/sulfur elemental ratio ranging from 2 to 10). Back trajectory analysis from Cloud-Aerosol Lidar with Orthogonal Polarization observations indicates that deep convection over the Indian subcontinent supplies the ATAL through the transport of pollution into the UTLS. Time series of deep convection occurrence, carbon monoxide, aerosol, temperature, and relative humidity suggest that secondary aerosol formation and growth in a cold, moist convective environment could play an important role in the formation of ATAL. Finally, radiative calculations show that the ATAL layer has exerted a short-term regional forcing at the top of the atmosphere of −0.1 W/m2 in the past 18 years. Key Points Increase of summertime upper tropospheric aerosol levels over Asia since the 1990s Upper tropospheric enhancement also observed by in situ backscatter measurements Significant regional radiative forcing of −0.1 W/m2

Hazardous thunderstorm intensification over Lake Victoria

Weather extremes have harmful impacts on communities around Lake Victoria, where thousands of fishermen die every year because of intense night-time thunderstorms. Yet how these thunderstorms will evolve in a future warmer climate is still unknown. Here we show that Lake Victoria is projected to be a hotspot of future extreme precipitation intensification by using new satellite-based observations, a high-resolution climate projection for the African Great Lakes and coarser-scale ensemble projections. Land precipitation on the previous day exerts a control on night-time occurrence of extremes on the lake by enhancing atmospheric convergence (74%) and moisture availability (26%). The future increase in extremes over Lake Victoria is about twice as large relative to surrounding land under a high-emission scenario, as only over-lake moisture advection is high enough to sustain Clausius–Clapeyron scaling. Our results highlight a major hazard associated with climate change over East Africa and underline the need for high-resolution projections to assess local climate change.

Geostationary Operational Environmental Satellite (GOES)-14 super rapid scan operations to prepare for GOES-R

Abstract Geostationary Operational Environmental Satellite (GOES)-14 imager was operated by National Oceanic and Atmospheric Administration (NOAA) in an experimental rapid scan 1-min mode that emulates the high-temporal resolution sampling of the Advanced Baseline Imager (ABI) on the next generation GOES-R series. Imagery with a refresh rate of 1 min of many phenomena were acquired, including clouds, convection, fires, smoke, and hurricanes, including 6 days of Hurricane Sandy through landfall. NOAA had never before operated a GOES in a nearly continuous 1-min mode for such an extended period of time, thereby making these unique datasets to explore the future capabilities possible with GOES-R. The next generation GOES-R imager will be able to routinely take mesoscale ( 1000     km × 1000     km ) images every 30 s (or two separate locations every minute). These images can be acquired even while scanning continental United States and full disk images. These high time-resolution images from the GOES-14 imager are being used to prepare for the GOES-R era and its advanced imager. This includes both the imagery and quantitative derived products such as cloud-top cooling. Several animations are included to showcase the rapid change of the many phenomena observed during super rapid scan operations for GOES-R (SRSOR).

On the Development of Above-Anvil Cirrus Plumes in Extratropical Convection

AbstractExpansive cirrus clouds present above the anvils of extratropical convection have been observed in satellite and aircraft-based imagery for several decades. Despite knowledge of their occurrence, the precise mechanisms and atmospheric conditions leading to their formation and maintenance are not entirely known. Here, the formation of these cirrus “plumes” is examined using a combination of satellite imagery, four-dimensional ground-based radar observations, assimilated atmospheric states from a state-of-the-art reanalysis, and idealized numerical simulations with explicitly resolved convection. Using data from 20 recent events (2013–present), it is found that convective cores of storms with above-anvil cirrus plumes reach altitudes 1–6 km above the tropopause. Thus, it is likely that these clouds represent the injection of cloud material into the lower stratosphere. Comparison of storms with above-anvil cirrus plumes and observed tropopause-penetrating convection without plumes reveals an associat...

In situ and space‐based observations of the Kelud volcanic plume: The persistence of ash in the lower stratosphere

Abstract Volcanic eruptions are important causes of natural variability in the climate system at all time scales. Assessments of the climate impact of volcanic eruptions by climate models almost universally assume that sulfate aerosol is the only radiatively active volcanic material. We report satellite observations from the Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite after the eruption of Mount Kelud (Indonesia) on 13 February 2014 of volcanic materials in the lower stratosphere. Using these observations along with in situ measurements with the Compact Optical Backscatter AerosoL Detector (COBALD) backscatter sondes and optical particle counters (OPCs) made during a balloon field campaign in northern Australia, we find that fine ash particles with a radius below 0.3 µm likely represented between 20 and 28% of the total volcanic cloud aerosol optical depth 3 months after the eruption. A separation of 1.5–2 km between the ash and sulfate plumes is observed in the CALIOP extinction profiles as well as in the aerosol number concentration measurements of the OPC after 3 months. The settling velocity of fine ash with a radius of 0.3 µm in the tropical lower stratosphere is reduced by 50% due to the upward motion of the Brewer‐Dobson circulation resulting a doubling of its lifetime. Three months after the eruption, we find a mean tropical clear‐sky radiative forcing at the top of the atmosphere from the Kelud plume near −0.08 W/m2 after including the presence of ash; a value ~20% higher than if sulfate alone is considered. Thus, surface cooling following volcanic eruptions could be affected by the persistence of ash and should be considered in climate simulations.

Terrestrial gamma ray flashes due to particle acceleration in tropical storm systems

Terrestrial gamma ray flashes (TGFs) are submillisecond flashes of energetic radiation that are believed to emanate from intracloud lightning inside thunderstorms. This emission can be detected hundreds of kilometers from the source by space-based observatories such as the Fermi Gamma-ray Space Telescope (Fermi). The location of the TGF-producing storms can be determined using very low frequency (VLF) radio measurements made simultaneously with the Fermi detection, allowing additional insight into the mechanisms which produce these phenomena. In this paper, we report 37 TGFs originating from tropical storm systems for the first time. Previous studies to gain insight into how tropical cyclones formed and how destructive they can be include the investigation of lightning flash rates and their dependence on storm evolution. We find TGFs to emanate from a broad range of distances from the storm centers. In hurricanes and severe tropical cyclones, the TGFs are observed to occur predominately from the outer rainbands. A majority of our sample also show TGFs occurring during the strengthening phase of the encompassing storm system. These results verify that TGF production closely follows when and where lightning predominately occurs in cyclones. The intrinsic characteristics of these TGFs were not found to differ from other TGFs reported in larger samples. We also find that some TGF-producing storm cells in tropical storm systems far removed from land have a low number of WWLLN sferics. Although not unique to tropical cyclones, this TGF/sferic ratio may imply a high efficiency for the lightning in these storms to generate TGFs.

Using Satellite Data to Improve Convective Forecasts in the Collaborative Storm Prediction for Aviation (CoSPA)

High quality weather forecasts are essential to minimizing delays in the National Airspace System. The goal of the Collaborative Storm Prediction System for Aviation (CoSPA) is to provide high resolution, rapidly-updating storm forecasts for air traffic management out to 8 hours. To achieve this goal, CoSPA will optimally blend heuristics and numerical weather prediction models into a unified set of aviation-specific storm forecast products with the best overall performance possible. Convective initiation remains a significant forecasting challenge in CoSPA. Satellite data can provide valuable information to aid forecasting of storm formation, particularly in the early portions of the forecast. This paper will present two techniques that address the use of satellite data to initiate convection in CoSPA. The first technique uses visible satellite and radar data to initiate convection in convective lines. The second technique uses infrared convective initiation interest fields from the SATellite Convection AnalySis and Tracking system to initiate convection in situations with little or no pre-existing radar precipitation.

A case study of convectively sourced water vapor observed in the overworld stratosphere over the United States

On August 27, 2013, during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission, NASAs ER-2 research aircraft encountered a region of enhanced water vapor, extending over a depth of approximately 2 km and a minimum areal extent of 20,000 km2 in the stratosphere (375 K to 415 K potential temperature), south of the Great Lakes (42°N, 90°W). Water vapor mixing ratios in this plume, measured by the Harvard Water Vapor instrument, constitute the highest values recorded in situ at these potential temperatures and latitudes. An analysis of geostationary satellite imagery in combination with trajectory calculations links this water vapor enhancement to its source, a deep tropopause-penetrating convective storm system that developed over Minnesota 20 hours prior to the aircraft plume encounter. High resolution, ground-based radar data reveal that this system was comprised of multiple individual storms, each with convective turrets that extended to a maximum of ~4 km above the tropopause level for several hours. In situ water vapor data show that this storm system irreversibly delivered between 6.6 kt and 13.5 kt of water to the stratosphere. This constitutes a 20 – 25% increase in water vapor abundance in a column extending from 115 hP to 70 hPa over the plume area. Both in situ and satellite climatologies show a high frequency of localized water vapor enhancements over the central U.S. in summer, suggesting that deep convection can contribute to the stratospheric water budget over this region and season.

BATAL: The Balloon Measurement Campaigns of the Asian Tropopause Aerosol Layer

AbstractWe describe and show results from a series of field campaigns that used balloonborne instruments launched from India and Saudi Arabia during the summers 2014–17 to study the nature, formati...

The Above-Anvil Cirrus Plume: An Important Severe Weather Indicator in Visible and Infrared Satellite Imagery

AbstractIntense tropopause-penetrating updrafts and gravity wave breaking generate cirrus plumes that reside above the primary anvil. These “above anvil cirrus plumes” (AACPs) exhibit unique temper...