Phys.org September 27, 2024 The complex interactions of hurricane intensity and precipitation and the impacts of improving hurricane dynamics on streamflow forecasts are not well established yet. Researchers at the University of Houston addressed these gaps by characterizing the role of vertical diffusion in improving hurricane intensity and streamflow forecasts under different planetary boundary layer, microphysics, and cumulus parameterizations. They coupled the Weather Research and Forecasting (WRF) atmospheric model with the WRF hydrological model to simulate four major hurricanes in three hurricane-prone regions in the United States. A stepwise calibration reduced streamflow forecast errors. 60 coupled hydrometeorological simulations evaluated the […]
Category Archives: Atmospheric science
Scientists discover a long-sought global electric field on Earth
Phys.org August 28, 2024 Observations of heated O+ ions in the magnetosphere are consistent with resonant wave–particle interactions. By contrast, observations of cold supersonic H+ flowing out of the polar wind suggest the presence of an electrostatic field. An international team of researchers (USA – NASA Goddard Space Flight Center, Catholic University of America, Embry-Riddle Aeronautical University, University of New Hampshire, University of Colorado at Boulder, UC Berkeley, Penn State University, NASA Wallops Flight Facility, UK, Norway, Sweden, Svalbard and Jan Mayen) described the existence of an electric potential drop between 250 km and 768 km from a planetary electrostatic field generated […]
Modern aircraft emit less carbon than older aircraft, but their contrails may do more environmental harm
Phys.org August 7, 2024 Contrails contribute over half of the positive radiative forcing from aviation, but the size of this warming effect is highly uncertain. In-situ observations have demonstrated an impact of aircraft and fuel type on contrail properties close to the aircraft, but there are few observational constraints at these longer timescales, despite these having a strong impact in high-resolution and global models. An international team of researchers (UK, Germany, USA – NASA Langley Research Center (VA)) found a relationship between aircraft type and contrail formation after investigating over 64 000 cases, with more efficient aircraft forming longer-lived satellite-detectable […]
New research underscores the close relationship between Saharan dust and hurricane rainfall
Phys.org July 24, 2024 The impact of global climate changes on Tropical Cyclone Rainfall (TCR) is complex and debatable. A team of researchers in the US (Western Michigan State University, Stanford University, Perdue University, University of Utah, Caltech) used an XGBoost machine learning model with 19-year meteorological data and hourly satellite precipitation observations to predict TCR for individual storms. The model identified dust optical depth (DOD) as a key predictor that enhances performance evidently. The model uncovered a nonlinear and boomerang-shape relationship between Saharan dust and TCR, with a TCR peak at 0.06 DOD and a sharp decrease thereafter. This […]
Raindrops grow with turbulence in clouds: New findings could improve weather and climate models
Phys.org July 25, 2024 A team of researchers in the US (NSF National Center for Atmospheric Research, industry) provided substantial evidence for significant impacts of turbulence on the evolution of cloud droplet size distributions and rain formation by comparing high-resolution observations of cumulus congestus clouds with state-of-the-art large-eddy simulations coupled with a Lagrangian particle-based microphysics scheme. Turbulence causes earlier rain formation and greater rain accumulation compared to simulations with gravitational coalescence only. The observed rain size distribution tail just above cloud base follows a power law scaling that deviates from theoretical scalings considering either a purely gravitation collision kernel or […]
Revealing the influences on La Niña and El Niño weather conditions
Phys.org July 31, 2024 Despite common background La Niña conditions, Australia was very dry in November 2020 and wet in November 2021. Researchers in Australia examined the El Niño Southern Oscillation, Indian Ocean Dipole, Southern Annular Mode and Madden Julian Oscillation, but they did not find obvious clues. They found that the absence (in 2020) or presence (in 2021) of an enhanced thermal wind and subtropical jet over the Australian continent contributed to the rainfall anomalies. In November 2021 the warm sea surface temperatures led to an enhanced meridional temperature gradient and subtropical jet over Australia. The enhanced jet provided […]
‘New El Niño’ discovered south of the equator
Phys.org July 22. 2024 An international team of researchers (India, Japan) simulated Interannual sea surface temperature (SST) variations in the subtropical-midlatitude Southern Hemisphere which are often associated with a circumpolar wavenumber-4 (W4) pattern. They found that incoming climatological solar radiation goes into a thinner (thicker) mixed layer, the shallower (deeper) mixed layer promotes surface warming (cooling) leading to positive (negative) SST anomalies, developing the SST-W4 pattern during austral summer. Due to the temperature difference between the mixed layer and the water below the mixed layer, anomalous latent heat fluxes, and disappearance of the overlying atmospheric W4 pattern cause the decay […]
Scientists find new way global air churn makes particles
Phys.org July 12, 2024 New particle formation in the free troposphere is a major source of cloud condensation nuclei globally. The prevailing view is that in the free troposphere, new particles are formed predominantly in convective cloud outflows. An international team of researchers (USA -Washington University, NASA Langley Research Center (VA), University of Colorado, NOAA (Boulder), National Center for Atmospheric Research, Boulder, Washington University in St. Louis, Austria) presented another mechanism using global observations. They found that during stratospheric air intrusion events, the mixing of descending ozone-rich stratospheric air with more moist free tropospheric background resulted in elevated hydroxyl radical […]
New twists on tornadoes: Earth scientist studies why U.S. has so many tornadoes
Phys.org June 27, 2024 Central North America is the global hotspot for tornadoes, fueled by elevated terrain of the Rockies to the west and a source of warm, moist air from equatorward oceans. Based on this theory central South America, with the Andes to the west and Amazon basin to the north, should have a “tornado alley” at least as active as central North America. Central South America has frequent severe thunderstorms yet relatively few tornadoes. According to a team of researchers in the US (Purdue University, National Center for Atmospheric Researchers, (Boulder, CO), Stony Brook University, Colorado State University) […]
New insights into the formation of tiny cloud particles in the Arctic
Phys.org June 21, 2024 Vertical particle distributions are required to study aerosol–cloud interaction over sea ice comprehensively. An international team of researchers (Germany, USA – University of Colorado) presented vertically resolved measurements of aerosol particle number concentrations and sizes using tethered balloons with the data collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition in the summer of 2020. Radiosoundings, cloud remote sensing data, and 5-day back trajectories supplemented the analysis of thirty-four profiles of aerosol particle number concentration observed in 2 particle size ranges above 150 nm (N>150). The majority of aerosol profiles showed more […]