Decoding atmospheric effects of gravity waves with high-res climate simulations

Phys.org  December 23, 2024 To understand the impact of mesoscale variability, including gravity waves (GWs), on atmospheric circulation, a team of researchers in the US (Stanford University, Oak Ridge National Laboratory) extracted data from four months of an integrated data at 1 km resolution (XNR1K) using the Integrated Forecast System (IFS) model. They computed zonal and meridional flux of vertical momentum from ~1.5 petabytes of data. The fluxes were validated using ERA5 reanalysis, both during the first week after initialization and over the boreal winter period from November 2018 to February 2019. The agreement between reanalysis and IFS demonstrated its […]

Longer records bring climate change’s impact on atmospheric circulation to light

Phys.org  December 23, 2024 The effects of climate change on atmospheric circulation are more complex because the atmosphere is noisy and chaotic and thermodynamic changes can generate effects that make circulation changes difficult to decipher. According to an international team of researchers (USA – University of Chicago, NOAA, Boulder CO, University of Virginia, Germany, Australia, Switzerland, Israel, Finland) the circulation signals are an opportunity for improving our understanding of dynamical mechanisms, testing our theories and reducing uncertainties. The signals have also presented puzzles that represent an opportunity for better understanding the circulation response to climate change, its contribution to climate […]

3D scans of giant hailstones reveal surprising discoveries that could help predict future storms

Phys.org  December 4, 2024 Researchers in Spain analyzed the stones collected during fieldwork to gather information on their growth processes. They analysed used Computed Tomography Scan, which was utilized to analyze hailstones and their interiors. They obtained a complete 3D view of the interior of the stone, without producing any alteration in the structure they quantified densities of different layers. The analysis helped verify previous theories that the nuclei can be placed far from the stone center even if the hailstone is externally spherical… read more. Open Access TECHNICAL ARTICLE

Enhancing hurricane forecasts: Simulations reveal reducing estimates of atmospheric friction improves storm predictions

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 […]

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 […]