Phys.org December 21, 2022 Dust entrained into the atmosphere serves as a major aerosol type, exerting effects on weather and climate system via aerosol-radiation-cloud interactions and delivering nutrients from continents to other continents and oceans. Using a physically-based dust emission model, an international team of researchers (China, Germany, USA – Texas A&M University) has shown that the weakening of surface wind and the increasing of vegetation cover and soil moisture have all contributed to the decline in dust activity during 2001 to 2017. The relative contributions of these three factors to the dust emission reduction during 2010–2017 relative to 2001 […]
Tag Archives: Atmospheric science
New kind of tropical cyclone identified in the Indian Ocean
Phys.org November 28, 2022 Researchers in Australia focused on the regional wind variability that controls the intensity of cold-water upwelling off Sumatra – a key feature of the Indian Ocean Dipole (IOD). Their analysis of daily atmospheric data revealed the existence of convectively triggered synoptic-scale atmospheric cyclones in the South-East Tropical Indian Ocean (SETIO). The northern branch of the cyclones corresponded to westerly equatorial wind events, whereas the eastern branch involved north-westerly winds that operate to suppress cold-water upwelling off Sumatra’s west coast. Data for the period 1988–2022 showed that 5–9 SETIO cyclones normally form each year during the boreal […]
Unabated Carbon Is Shrinking Earth’s Upper Atmosphere, Scientists Warn
Science Alert November 22, 2022 A team of researchers in the US (NASA Langley Research Center, industry, NCAR, University of Colorado, Catholic University of America, NASA Langley Research Center, Hampton University) examined the thermal structure of the mesosphere and lower thermosphere (MLT) using observations from 2002 through 2021 from the NASA satellite. They showed that the MLT has significantly cooled and contracted between the years 2002 and 2019 due to a combination of a decline in the intensity of the 11-year solar cycle and increasing CO2. During this time the thickness of atmosphere between approximately 48 and 105 km has […]
The lightness of water vapor adds heft to global climate models
Science Daily October 24, 2022 The molar mass of water vapour is less than that of dry air, making humid air lighter than dry air at the same temperature and pressure. This effect is known as vapour buoyancy and has been considered negligibly small in large-scale climate dynamics. Using theory, reanalysis data and a hierarchy of climate models a team of researchers in the US (UC Davis, Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory) showed that vapour buoyancy has a similar magnitude to thermal buoyancy in the tropical free troposphere. They also showed that vapour buoyancy makes cold air […]
Tracking raindrops, one molecule at a time
Science Daily October 25, 2022 A team of researchers in the US (U Mass. Amherst, University of Alaska) studied the mechanisms of precipitation deuterium excess (d-excess) seasonality in low-latitudes and mid-latitudes through a new analysis of precipitation isotope databases along with climate reanalysis products and moisture tracking models. The ultimate d-excess signals are produced after complex modulations by several reinforcing or competing processes. They developed a simple seasonal water storage model to show that contributions of previously evaporated residual water storage and higher transpiration fractions may lead to relatively low d-excess in evapotranspiration fluxes during periods of enhanced continental moisture […]
To Better Predict Extreme Precipitation, Scientists Model Cloud Microphysics
EureakAlert October 5, 2022 Microphysics processes, which include the formation and breakup of liquid droplets and ice crystals, cannot be directly simulated in climate models because of their small spatial scales. Thus, models must simulate their net effect on clouds indirectly. A team of researchers in the US (Lawrence Berkeley National Laboratory, UC Irvine) investigated multiple ways of doing this and examined the resultant effect on rainfall extremes. While feedbacks onto large-scale weather patterns are important globally as they were in CONUS, significant local effects manifest in the tropics. For instance, the more comprehensive (2-moment) microphysics scheme produces clouds associated […]
Elusive atmospheric wave detected during Tonga volcanic eruption
Phys.org September 19, 2022 Using state-of-the-art observational data and computer simulations an international team of researchers (Japan, USA -University of Hawaii) discovered the existence of Pekeris waves—fluctuations in air pressure that were theorized in 1937 but never proven to occur in nature, till after the Tonga eruption. The atmospheric wave pattern close to the eruption was quite complicated, but thousands of miles away the disturbances were led by an isolated wave front traveling horizontally at more than 650 miles per hour as it spread outward. The air pressure perturbations associated with the initial wave front were seen clearly on thousands […]
New information on ‘gigantic jet’ lightning bursts that reach toward space
Phys.org August 8, 2022 Occasionally, lightning will exit the top of a thunderstorm and connect to the lower edge of space, forming a gigantic jet. An international team of researchers (USA – Georgia Institute of Technology, research org., Texas Tech University, University of New Hampshire, Duke University, University of Oklahoma, Los Alamos National Laboratory, Spain) reports on observations of a negative gigantic jet that transferred an extraordinary amount of charge between the troposphere and ionosphere (∼300 C). It occurred in unusual circumstances, emerging from an area of weak convection. As the discharge ascended from the cloud top, tens of very […]
A cloudless future? The mystery at the heart of climate forecasts
Science Daily May 31, 2022 Analyses of global climate models consistently show that clouds constitute the biggest source of uncertainty and instability. But they occur on a length- and timescale that today’s models can’t come close to reproducing. Therefore, they included in models through a variety of approximations. A team of researchers in the US (UC Irvine, Lawrence Livermore National Laboratory, University of Washington, industry) is working to fix this glaring gap by breaking the climate modeling problem into two parts: a coarse-grained, lower-resolution (100km) planetary model and many small patches with 100 to 200 meter resolution. They developed a […]
A proposal to use electric charges to encourage raindrops to form in clouds
Phys.org February 9, 2022 Researchers in the UK calculated the electrostatic forces between two water spheres that have not yet grown large enough to be described as raindrops. They found that the greater the variation in charges between droplets, the stronger the attraction between them. And that led them to suggest that if the variation was increased via an electric charge, the droplets would merge, leading to the formation of rain drops. As droplets merge and grow in size, additional electric charge should result in mergers between droplets until they become large enough for gravity to take over and they […]