scholarly journals Pseudovertical Temperature Profiles Give Insight into Winter Evolution of the Atmospheric Boundary Layer over the McMurdo Dry Valleys of Antarctica

2013 ◽  
Vol 52 (7) ◽  
pp. 1664-1669 ◽  
Author(s):  
Peyman Zawar-Reza ◽  
Marwan Katurji ◽  
Iman Soltanzadeh ◽  
Tanja Dallafior ◽  
Shiyuan Zhong ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Weather Prediction ◽  
Atmospheric Temperature ◽  
Numerical Weather Prediction Model ◽  
Mcmurdo Dry Valleys ◽  
Dry Valleys ◽  
Cold Pools ◽  
Routine Monitoring ◽  
Strong Winds

AbstractMeasuring routine vertical profiles of atmospheric temperature is critical in understanding stability and the dynamics of the boundary layer. Routine monitoring in remote areas such as the McMurdo Dry Valleys (MDV) of Antarctica is logistically difficult and expensive. Pseudovertical profiles that were derived from a network of inexpensive ground temperature sensors planted on valley sidewalls (up to 330 m above valley floor), together with data from a weather station and a numerical weather prediction model, provided a long-term climatological description of the evolution of the winter boundary layer over the MDV. In winter, persistent valley cold pools (VCPs) were common, lasting up to 2 weeks. The VCPs were eroded by warm-air advection from aloft associated with strong winds, increasing the temperature of the valley by as much as 25 K. Pseudovertical datasets as described here can be used for model validation.

scholarly journals Distinguishing the Cold Conveyor Belt and Sting Jet Airstreams in an Intense Extratropical Cyclone

2014 ◽  
Vol 142 (8) ◽  
pp. 2571-2595 ◽  
Author(s):  
Oscar Martínez-Alvarado ◽  
Laura H. Baker ◽  
Suzanne L. Gray ◽  
John Methven ◽  
Robert S. Plant
Keyword(s):  
Weather Prediction ◽  
Conveyor Belt ◽  
Numerical Weather Prediction Model ◽  
Strong Wind ◽  
Air Masses ◽  
Mesoscale Structures ◽  
Mesoscale Structure ◽  
Chemical Tracer ◽  
Strong Winds ◽  
First Time

Abstract Strong winds equatorward and rearward of a cyclone core have often been associated with two phenomena: the cold conveyor belt (CCB) jet and sting jets. Here, detailed observations of the mesoscale structure in this region of an intense cyclone are analyzed. The in situ and dropsonde observations were obtained during two research flights through the cyclone during the Diabatic Influences on Mesoscale Structures in Extratropical Storms (DIAMET) field campaign. A numerical weather prediction model is used to link the strong wind regions with three types of “airstreams” or coherent ensembles of trajectories: two types are identified with the CCB, hooking around the cyclone center, while the third is identified with a sting jet, descending from the cloud head to the west of the cyclone. Chemical tracer observations show for the first time that the CCB and sting jet airstreams are distinct air masses even when the associated low-level wind maxima are not spatially distinct. In the model, the CCB experiences slow latent heating through weak-resolved ascent and convection, while the sting jet experiences weak cooling associated with microphysics during its subsaturated descent. Diagnosis of mesoscale instabilities in the model shows that the CCB passes through largely stable regions, while the sting jet spends relatively long periods in locations characterized by conditional symmetric instability (CSI). The relation of CSI to the observed mesoscale structure of the bent-back front and its possible role in the cloud banding is discussed.

scholarly journals Intrinsic Predictability of the 20 May 2013 Tornadic Thunderstorm Event in Oklahoma at Storm Scales

2016 ◽  
Vol 144 (4) ◽  
pp. 1273-1298 ◽  
Author(s):  
Yunji Zhang ◽  
Fuqing Zhang ◽  
David J. Stensrud ◽  
Zhiyong Meng
Keyword(s):  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Lead Times ◽  
Forecast Errors ◽  
Ensemble Forecasts ◽  
Positive Feedbacks ◽  
Convective Storms ◽  
Cold Pools ◽  
Initial Errors ◽  
Environmental Instability

Abstract Using a high-resolution convection-allowing numerical weather prediction model, this study seeks to explore the intrinsic predictability of the severe tornadic thunderstorm event on 20 May 2013 in Oklahoma from its preinitiation environment to initiation, upscale organization, and interaction with other convective storms. This is accomplished through ensemble forecasts perturbed with minute initial condition uncertainties that were beyond detection capabilities of any current observational platforms. It was found that these small perturbations, too small to modify the initial mesoscale environmental instability and moisture fields, will be propagated and evolved via turbulence within the PBL and rapidly amplified in moist convective processes through positive feedbacks associated with updrafts, phase transitions of water species, and cold pools, thus greatly affecting the appearance, organization, and development of thunderstorms. The forecast errors remain nearly unchanged even when the initial perturbations (errors) were reduced by as much as 90%, which strongly suggests an inherently limited predictability for this thunderstorm event for lead times as short as 3–6 h. Further scale decomposition reveals rapid error growth and saturation in meso-γ scales (regardless of the magnitude of initial errors) and subsequent upscale growth into meso-β scales.

Simulating boundary-layer rolls with a numerical weather prediction model

2015 ◽  
Vol 142 (694) ◽  
pp. 211-223 ◽  
Author(s):  
William Thurston ◽  
Robert J. B. Fawcett ◽  
Kevin J. Tory ◽  
Jeffrey D. Kepert
Keyword(s):  
Boundary Layer ◽  
Prediction Model ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Numerical Weather

Episodic basin-scale soil moisture anomalies associated with high relative humidity events in the McMurdo Dry Valleys, Antarctica

2021 ◽  
pp. 1-15
Author(s):  
Joseph Levy
Keyword(s):  
Soil Moisture ◽  
Relative Humidity ◽  
Mcmurdo Dry Valleys ◽  
Limiting Factor ◽  
High Humidity ◽  
Dry Valleys ◽  
Surface Soils ◽  
Basin Scale ◽  
Soil Reflectance

Abstract Outside of hydrologically wetted active layer soils and humidity-sensitive soil brines, low soil moisture is a limiting factor controlling biogeochemical processes in the McMurdo Dry Valleys. But anecdotal field observations suggest that episodic wetting and darkening of surface soils in the absence of snowmelt occurs during high humidity conditions. Here, I analyse long-term meteorological station data to determine whether soil-darkening episodes are present in the instrumental record and whether they are, in fact, correlated with relative humidity. A strong linear correlation is found between relative humidity and soil reflectance at the Lake Bonney long-term autonomous weather station. Soil reflectance is found to decrease annually by a median of 27.7% in response to high humidity conditions. This magnitude of darkening is consistent with soil moisture rising from typical background values of < 0.5 wt.% to 2–3 wt.%, suggesting that regional atmospheric processes may result in widespread soil moisture generation in otherwise dry surface soils. Temperature and relative humidity conditions under which darkening is observed occur for hundreds of hours per year, but are dominated by episodes occurring between midnight and 07h00 local time, suggesting that wetting events may be common, but are not widely observed during typical diel science operations.

Evaluation of the Rapid Refresh Numerical Weather Prediction Model Over Arctic Alaska

2021 ◽  
Author(s):  
Matthew T. Bray ◽  
David D. Turner ◽  
Gijs de Boer
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Numerical Weather ◽  
Arctic Alaska ◽  
Short Term Forecasting ◽  
Northern Alaska ◽  
Mixed Phase Clouds

AbstractDespite a need for accurate weather forecasts for societal and economic interests in the U.S. Arctic, thorough evaluations of operational numerical weather prediction in the region have been limited. In particular, the Rapid Refresh Model (RAP), which plays a key role in short-term forecasting and decision making, has seen very limited assessment in northern Alaska, with most evaluation efforts focused on lower latitudes. In the present study, we verify forecasts from version 4 of the RAP against radiosonde, surface meteorological, and radiative flux observations from two Arctic sites on the northern Alaskan coastline, with a focus on boundary-layer thermodynamic and dynamic biases, model representation of surface inversions, and cloud characteristics. We find persistent seasonal thermodynamic biases near the surface that vary with wind direction, and may be related to the RAP’s handling of sea ice and ocean interactions. These biases seem to have diminished in the latest version of the RAP (version 5), which includes refined handling of sea ice, among other improvements. In addition, we find that despite capturing boundary-layer temperature profiles well overall, the RAP struggles to consistently represent strong, shallow surface inversions. Further, while the RAP seems to forecast the presence of clouds accurately in most cases, there are errors in the simulated characteristics of these clouds, which we hypothesize may be related to the RAP’s treatment of mixed-phase clouds.

scholarly journals Validation of Precipitable Water Vapor within the NCEP/DOE Reanalysis Using Global GPS Observations from One Decade

2010 ◽  
Vol 23 (7) ◽  
pp. 1675-1695 ◽  
Author(s):  
Sibylle Vey ◽  
Reinhard Dietrich ◽  
Axel Rülke ◽  
Mathias Fritsche ◽  
Peter Steigenberger ◽  
...  
Keyword(s):  
Time Series ◽  
Water Vapor ◽  
Seasonal Cycle ◽  
Weather Prediction ◽  
Precipitable Water ◽  
Atmospheric Temperature ◽  
Interannual Variations ◽  
Seasonal Signals ◽  
The Tropics

Abstract In contrast to previous studies validating numerical weather prediction (NWP) models using observations from the global positioning system (GPS), this paper focuses on the validation of seasonal and interannual variations in the water vapor. The main advantage of the performed validation is the independence of the GPS water vapor estimates compared to studies using water vapor datasets from radiosondes or satellite microwave radiometers that are already assimilated into the NWP models. Tropospheric parameters from a GPS reanalysis carried out in a common project of the Technical Universities in Munich and Dresden were converted into precipitable water (PW) using surface pressure observations from the WMO and mean atmospheric temperature data from ECMWF. PW time series were generated for 141 globally distributed GPS sites covering the time period from the beginning of 1994 to the end of 2004. The GPS-derived PW time series were carefully examined for their homogeneity. The validation of the NWP model from NCEP shows that the differences between the modeled and observed PW values are time dependent. In addition to establishing a long-term mean, this study also validates the seasonal cycle and interannual variations in the PW. Over Europe and large parts of North America the seasonal cycle and the interannual variations in the PW from GPS and NCEP agree very well. The results reveal a submillimeter accuracy of the GPS-derived PW anomalies. In the regions mentioned above, NCEP provides a highly accurate database for studies of long-term changes in the atmospheric water vapor. However, in the Southern Hemisphere large differences in the seasonal signals and in the PW anomalies were found between GPS and NCEP. The seasonal signal of the PW is underestimated by NCEP in the tropics and in Antarctica by up to 40% and 25%, respectively. Climate change studies based on water vapor data from NCEP should consider the large uncertainties in the analysis when interpreting these data, especially in the tropics.

scholarly journals STUDY ON VERTICAL STRUCTURE OF MARINE BOUNDARY LAYER OVER PALAU

2016 ◽  
Vol 2 (6) ◽  
Author(s):  
S Venkata Raju ◽  
K Madhusudhana
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Weather Prediction ◽  
Thermodynamic Characteristics ◽  
Free Atmosphere ◽  
Marine Stratocumulus ◽  
Oceanic Surface ◽  
Moisture Fluxes ◽  
Republic Of Palau

Atmospheric Boundary Layer (ABL) over land and ocean surface is quite diriment because of the differing dynamic and thermodynamic characteristics of both the surface. The structure and characteristics of the ABL over the oceanic surface, often known as the Marine Boundary Layer (MBL) plays an important role in regulating the surface energy, moisture fluxes and in controlling the convective transfer of energy moisture of the free atmosphere. It is imperative for coupled ocean-atmosphere modelling and numerical weather prediction. PALAU (Pacific Area Long-term Atmospheric observation for the Understanding of climate change) over Aimeliik state of Babeldaob Island (7.45° N; 134.47° E) of Republic of Palau field study can advances our knowledge of marine stratocumulus by providing information on the boundary layer and cloud structure, as well as their diurnal cycle.

scholarly journals Spectral Recalibration of NOAA HIRS Longwave CO2 Channels toward a 40+ Year Time Series for Climate Studies

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1317
Author(s):  
Bin Zhang ◽  
Changyong Cao ◽  
Tung-Chang Liu ◽  
Xi Shao
Keyword(s):  
Time Series ◽  
Spectral Response ◽  
Weather Prediction ◽  
Weather Forecast ◽  
Atmospheric Temperature ◽  
Spectral Shift ◽  
University Of Wisconsin ◽  
Science Community ◽  
The University

The High-Resolution Infrared Radiation Sounder (HIRS) on NOAA and MetOp A/B satellites has been observing the Earth continuously for over four decades, providing essential data for operational numerical weather prediction, retrieval of atmospheric vertical profile, and total column information on atmospheric temperature, moisture, water vapor, ozone, cloud climatology, and other geophysical parameters globally. Although the HIRS data meets the needs of the short-term weather forecast, there are inconsistencies when the long-term decadal time series is used for time series analysis. The discrepancies are caused by several factors, including spectral response differences between the HIRS models on the satellites and spectral response uncertainties and other calibration issues. Previous studies have demonstrated that significant improvements can be achieved by recalibrating some of the HIRS longwave CO2 channels (Channels 4, 5, 6, and 7), which has helped make the time series more consistent. The current study aims to extend the previous study to the remaining longwave infrared sounding channels, including Channels 1, 2, 3, and 8, using a similar approach. Similar to previous findings, the spectral shift of the HIRS bands has helped improve the consistency in the time series from NOAA-06 to MetOp-A and B for these channels. We also found that HIRS channels on MetOp-B also have bias relative to Infrared Atmospheric Sounding Interferometer (IASI) on the same satellite, especially Channel 4, and a spectral shift significantly reduced the bias. To bridge the observation gap in time series in the mid-1980s between NOAA-07 and NOAA-09, the global mean method has been used since no transfer radiometers between them was available for this period, and the spectral response function corrections, therefore, can be applied to the earliest satellites (NOAA-06) for these channels. The recalibration parameters have been provided to other scientists at the University of Wisconsin for improving the time series in their long-term studies using historical HIRS data and are now made available to the science community.

scholarly journals Representation of the grey zone of turbulence in the atmospheric boundary layer

2016 ◽  
Vol 13 ◽  
pp. 63-67 ◽  
Author(s):  
Rachel Honnert
Keyword(s):  
Boundary Layer ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Grey Zone ◽  
Shallow Convection ◽  
Convective Boundary ◽  
Boundary Layer Height ◽  
Eddy Simulation ◽  
Layer Structures ◽  
Large Eddy

Abstract. Numerical weather prediction model forecasts at horizontal grid lengths in the range of 100 to 1 km are now possible. This range of scales is the "grey zone of turbulence". Previous studies, based on large-eddy simulation (LES) analysis from the MésoNH model, showed that some assumptions of some turbulence schemes on boundary-layer structures are not valid. Indeed, boundary-layer thermals are now partly resolved, and the subgrid remaining part of the thermals is possibly largely or completely absent from the model columns. First, some modifications of the equations of the shallow convection scheme have been tested in the MésoNH model and in an idealized version of the operational AROME model at resolutions coarser than 500 m. Secondly, although the turbulence is mainly vertical at mesoscale (>  2 km resolution), it is isotropic in LES (<  100 m resolution). It has been proved by LES analysis that, in convective boundary layers, the horizontal production of turbulence cannot be neglected at resolutions finer than half of the boundary-layer height. Thus, in the grey zone, fully unidirectional turbulence scheme should become tridirectional around 500 m resolution. At Météo-France, the dynamical turbulence is modelled by a K-gradient in LES as well as at mesoscale in both MésoNH and AROME, which needs mixing lengths in the formulation. Vertical and horizontal mixing lengths have been calculated from LES of neutral and convective cases at resolutions in the grey zone.

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