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 […]
Tag Archives: Atmospheric science
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 […]
‘Rivers’ in the sky likely to drench East Asia under climate change
Phys.org January 18, 2022 Intense atmospheric rivers (ARs), eddy transports of moisture over the middle latitudes, contributed significantly to the extremely heavy rainfall events over the last decade in parts of East Asia. The extent to which ARs produce extreme rainfall over East Asia in a warmer climate remains unclear. An international team of researchers (Japan, USA – University of North Carolina) evaluated changes in the frequency and intensity of AR-related extreme heavy rainfall under global warming using a set of high-resolution global and regional atmospheric simulations. They found that both the AR-related water vapor transport and rainfall intensify over […]
Weather balloon data shows troposphere getting thicker, pushing tropopause higher over past 40 years
Phys.org November 8, 2021 Tropopause height (H) is a sensitive diagnostic for anthropogenic climate change. Previous studies showed increases in H over 1980–2000 but were inconsistent in projecting H trends after 2000. While H generally responds to temperature changes in the troposphere and stratosphere, the relative importance of these two contributions is uncertain. An international team of researchers (China, Canada, USA – NCAR, Boulder CO, Austria) used radiosonde balloon observations in the Northern Hemisphere (NH) over 20°N to 80°N to reveal a continuous rise of H over 1980–2020. Over 2001–2020, H increases at 50 to 60 m/decade, which is comparable […]
Global satellite data shows clouds will amplify global heating
Phys.org July 19, 2021 Researchers in the UK used data from Earth observations and climate model simulations to develop a statistical learning analysis of how clouds respond to changes in the environment. They showed that global cloud feedback is dominated by the sensitivity of clouds to surface temperature and tropospheric stability. Considering changes in just these two factors, they were able to constrain global cloud feedback to 0.43 ± 0.35 W⋅m−2⋅K−1 (90% confidence), implying a robustly amplifying effect of clouds on global warming and only a 0.5% chance of Equilibrium Climate Sensitivity below 2 K. The “cloud feedback” is the […]