scholarly journals Stable Atmospheric Boundary Layers and Diurnal Cycles: Challenges for Weather and Climate Models

2013 ◽  
Vol 94 (11) ◽  
pp. 1691-1706 ◽  
Author(s):  
A. A. M. Holtslag ◽  
G. Svensson ◽  
P. Baas ◽  
S. Basu ◽  
B. Beare ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Climate Models ◽  
Model Performance ◽  
Weather Forecast ◽  
The Arctic ◽  
Diurnal Cycles ◽  
Low Wind Speed ◽  
Weather And Climate

The representation of the atmospheric boundary layer is an important part of weather and climate models and impacts many applications such as air quality and wind energy. Over the years, the performance in modeling 2-m temperature and 10-m wind speed has improved but errors are still significant. This is in particular the case under clear skies and low wind speed conditions at night as well as during winter in stably stratified conditions over land and ice. In this paper, the authors review these issues and provide an overview of the current understanding and model performance. Results from weather forecast and climate models are used to illustrate the state of the art as well as findings and recommendations from three intercomparison studies held within the Global Energy and Water Exchanges (GEWEX) Atmospheric Boundary Layer Study (GABLS). Within GABLS, the focus has been on the examination of the representation of the stable boundary layer and the diurnal cycle over land in clear-sky conditions. For this purpose, single-column versions of weather and climate models have been compared with observations, research models, and large-eddy simulations. The intercomparison cases are based on observations taken in the Arctic, Kansas, and Cabauw in the Netherlands. From these studies, we find that even for the noncloudy boundary layer important parameterization challenges remain.

The Impact of Mixed-Phase Microphysical Processes on the Turbulence in Low-level Clouds in the Arctic

2021 ◽  
Author(s):  
Jan Chylik ◽  
Roel Neggers
Keyword(s):  
Boundary Layer ◽  
Climate Models ◽  
Weather Forecast ◽  
Mixed Phase ◽  
The Arctic ◽  
Contributing Factors ◽  
Microphysics Scheme ◽  
Low Level ◽  
Microphysical Processes ◽  
The Impact

<p>The proper representation of Arctic mixed-phased clouds remains a challenge in both weather forecast and climate models. Amongst the contributing factors is the complexity of turbulent properties of clouds. While the effect of evaporating hydrometeors on turbulent properties of the boundary layer has been identified in other latitudes, the extent of similar studies in the Arctic has been so far limited.</p><p>Our study focus on the impact of heat release from mixed-phase microphysical processes on the turbulent properties of the convective low-level clouds in the Arctic. We  employ high-resolution simulations, properly constrained by relevant measurements.<br>Semi-idealised model cases are based on convective clouds observed during the recent campaign in the Arctic: ACLOUD, which took place May--June 2017 over Fram Strait. The simulations are performed in Dutch Atmospheric Large Eddy Simulation (DALES) with double-moment mixed-phase microphysics scheme of Seifert & Beheng.</p><p>The results indicate an enhancement of boundary layer turbulence is some convective regimes.<br>Furthermore, results are sensitive to aerosols concentrations. Additional implications for the role of mixed-phase clouds in the Arctic Amplification will be discussed.</p>

Characterizing the atmospheric boundary layer over Disko Bay: local structure and links to global dynamics

2021 ◽  
Author(s):  
Arno Hammann ◽  
Kirsty Langley
Keyword(s):  
Climate Change ◽  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Large Scale ◽  
Climate Models ◽  
Current Knowledge ◽  
The Arctic ◽  
Global Dynamics ◽  
Ecosystem Monitoring ◽  
Reanalysis Dataset

<p>Surface air temperatures have been rising roughly twice as fast in the Arctic as in the global average (“Arctic amplification”). Not all responsible physical mechanisms are understood or known, and current climate models frequently underestimate the pace of Arctic warming. Knowledge is lacking specifically about processes involving moisture and the formation of clouds in the the atmospheric boundary layer (ABL). This reduces the reliability of Arctic and global climate change projections and short-term weather predictions.</p><p>We use a comprehensive multi-sensor observational dataset from the Greenland Ecosystem Monitoring (GEM, https://g-e-m.dk/) research site in Qeqertarsuaq, Greenland, in order to identify dominant structural and dynamic patterns of the ABL. Central to this dataset are the atmospheric column profiles of air temperature and water content acquired by a passive microwave radiometer, one of only three such instruments operating in Greenland. The in situ data is related to the large-scale circulation via an analysis of the global ERA5 reanalysis dataset, with a focus on moisture transport from humid latitudes.</p><p>The statistical analysis comprises both process-level relationships between observed variables (regressions) for individual events and pattern recognition techniques (clustering) for the identification of dominant patterns on the small and large scale, an approach particularly suited for the study of an unsteady, changing climate. Moisture enters the Arctic in narrow and infrequent atmospheric bands termed atmospheric rivers, and climate change may alter the frequency of such events, but also the thermodynamic reaction of the ABL to the moisture influx. The current knowledge of the cloudy polar ABL is insufficient to predict important aspects of its behavior, e.g. the lifetime of clouds and the strength of their radiative effect, as well as how large-scale atmospheric dynamics and the presence of elevated inversion layers interact with the structure of the ABL.</p>

scholarly journals On the u☆-U Relationship in the Stable Atmospheric Boundary Layer over Arctic Sea Ice

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 591
Author(s):  
Dmitry Chechin
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Sea Ice ◽  
Atmospheric Boundary Layer ◽  
Drag Coefficient ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Hockey Stick ◽  
Arctic Sea ◽  
Stable Atmospheric Boundary Layer

A relationship between the friction velocity u☆ and mean wind speed U in a stable atmospheric boundary layer (ABL) over Arctic sea ice was considered. To that aim, the observations collected during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment were used. The observations showed the so-called “hockey-stick” shape of the u☆−U relationship, which consists of a slow increase of u☆ with increasing wind speed for U<Utr and a more rapid almost linear increase of u☆ for U>Utr, where Utr is the wind speed of transition between the two regimes. Such a relationship is most pronounced at the highest observational levels, namely at 9 and 14 m, and is also sharper when the air-surface temperature difference exceeds its average values for stable conditions. It is shown that the Monin–Obukhov similarity theory (MOST) reproduces the observed u☆−U relationship rather well. This suggests that at least for the SHEBA dataset, there is no contradiction between MOST and the “hockey-stick” shape of the u☆−U relationship. However, the SHEBA data, as well as the single-column simulations show that for cases with strong stability, u☆ significantly decreases with height due to the shallowness of the ABL. It was shown that when u☆ was assumed independent of height, the value of the normalized drag coefficient, i.e., of the so-called stability correction function for momentum, calculated using observations at a certain level, can be significantly underestimated. To overcome this, the decrease of u☆ with height was taken into account in the framework of MOST using local scaling instead of the scaling with surface fluxes. Using such an extended MOST brought the estimates of the normalized drag coefficient closer to the Businger–Dyer relation.

Large Eddy Simulations of the Arctic atmospheric boundary layer around the MOSAiC drift track

2020 ◽  
Author(s):  
Daniela Littmann ◽  
Wolfgang Dorn ◽  
Hélène Bresson ◽  
Marion Maturilli ◽  
Markus Rex
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Observational Data ◽  
Global Climate ◽  
Weather Forecast ◽  
The Arctic ◽  
Climate Data ◽  
Surface Conditions ◽  
Large Eddy Simulation Model ◽  
Large Eddy

&lt;p&gt;The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) is the largest one-year-long research expedition within the central Arctic and has started in September 2019 to gather comprehensive climate data from an almost unreachable region. The gathered observational data in combination with concurrent high-resolution modeling provide new insights that play a key role for the improvement of our understanding of the interaction processes between the atmosphere, ocean, and sea ice and eventually global climate change. The present study focuses on the influence of the surface conditions on the atmospheric boundary layer by applying the large eddy simulation model configuration of the icosahedral non-hydrostatic model (ICON-LES). ICON-LES is used here with a grid spacing between 50 m and 800 m and set up to a domain with radii of 10 km to 100 km around the MOSAiC drift track. The model is driven by output data from weather forecast simulations for selected stormy and rather calm days. Results of simulations with various spatial horizontal resolutions and with different surface conditions such as ice fraction, ice thickness, snow cover will be compared and evaluated against observational data from MOSAiC.&lt;/p&gt;

scholarly journals Analysis of the performance of a ship-borne scanning wind lidar in the Arctic and Antarctic

2018 ◽  
Author(s):  
Rolf Zentek ◽  
Svenja H. E. Kohnemann ◽  
Günther Heinemann
Keyword(s):  
Boundary Layer ◽  
Quality Control ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Temporal Resolution ◽  
The Arctic ◽  
High Temporal Resolution ◽  
Doppler Lidar ◽  
Individual Measurement ◽  
Lidar Measurements

Abstract. Profiles of wind speed and direction at high spatial and temporal resolution are fundamental meteorological quantities for studies of the atmospheric boundary layer. Ship-based Doppler lidar measurements can contribute to fill the data gap over oceans particularly in polar regions. In the present study a non-motion stabilized scanning Doppler lidar was operated on board of RV Polarstern in the Arctic (June 2014) and Antarctic (December–January 2015/2016). This is the first time that such a system measured on an icebreaker in the Antarctic. A method for a motion correction of the data in the post-processing is presented. The wind calculation is based on vertical azimuth display (VAD) scans with eight directions that pass a quality control. Additionally a method for an empirical signal-to-noise ratio (SNR) threshold is presented, which can be calculated for individual measurement setups. Lidar wind profiles are compared to total of about 120 radiosonde profiles and also to wind measurements of the ship. The performance of the lidar measurements in comparison with radio soundings shows generally small RMSD (bias) for wind speed of around 1 m s−1 (0.1 m s−1) and for wind direction of around 12° (6°). The postprocessing of the non-motion stabilized data shows a comparable good quality as studies with motion stabilized systems. Two case studies show that a flexible change of SNR can be beneficial for special situations. Further the studies reveal that short-lived Low-Level Jets in the atmospheric boundary layer can be captured by lidar measurements with a high temporal resolution in contrast to routine radio soundings. The present study shows that a non-motion stabilized Doppler lidar can be operated successfully on an icebreaker. It presents a processing chain including quality control tests and error quantification, which is useful for further measurement campaigns.

Evaluation of regional NWP results for sea ice covered Bothnia Bay (Baltic Sea) in winter 2020.

2021 ◽  
Author(s):  
Marta Wenta ◽  
Agnieszka Herman
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Sea Ice ◽  
Surface Temperature ◽  
Atmospheric Boundary Layer ◽  
Baltic Sea ◽  
Polar Regions ◽  
Near Surface ◽  
Accurate Representation ◽  
Complex Processes

&lt;p&gt;The ongoing development of NWP (Numerical Weather Prediction) models and their increasing horizontal resolution have significantly improved forecasting capabilities. However, in the polar regions models struggle with the representation of near-surface atmospheric properties and the vertical structure of the atmospheric boundary layer (ABL) over sea ice. Particularly difficult to resolve are near-surface temperature, wind speed, and humidity, along with diurnal changes of those properties. Many of the complex processes happening at the interface of sea ice and atmosphere, i.e. vertical fluxes, turbulence, atmosphere - surface coupling are poorly parameterized or not represented in the models at all. Limited data coverage and our poor understanding of the complex processes taking place in the polar ABL limit the development of suitable parametrizations. We try to contribute to the ongoing effort to improve the forecast skill in polar regions through the analysis of unmanned aerial vehicles (UAVs) and automatic weather station (AWS) atmospheric measurements from the coastal area of Bothnia Bay (Wenta et. al., 2021), and the application of those datasets for the analysis of regional NWP models' forecasts.&amp;#160;&lt;/p&gt;&lt;p&gt;Data collected during HAOS (Hailuoto Atmospheric Observations over Sea ice) campaign (Wenta et. al., 2021) is used for the evaluation of regional NWP models results from AROME (Applications of Research to Operations at Mesoscale) - Arctic, HIRLAM (High Resolution Limited Area Model) and WRF (Weather Research and Forecasting). The presented analysis focuses on 27 Feb. 2020 - 2 Mar. 2020, the time of the HAOS campaign, shortly after the formation of new, thin sea ice off the westernmost point of Hailuoto island.&amp;#160; Throughout the studied period weather conditions changed from very cold (-14&amp;#8451;), dry and cloud-free to warmer (~ -5&amp;#8451;), more humid and opaquely cloudy. We evaluate models&amp;#8217; ability to correctly resolve near-surface temperature, humidity, and wind speed, along with vertical changes of temperature and humidity over the sea ice. It is found that generally, models struggle with an accurate representation of surface-based temperature inversions, vertical variations of humidity, and temporal wind speed changes. Furthermore, a WRF Single Columng Model (SCM) is launched to study whether specific WRF planetary boundary layer parameterizations (MYJ, YSU, MYNN, QNSE), vertical resolution, and more accurate representation of surface conditions increase the WRF model&amp;#8217;s ability to resolve the ABL above sea ice in the Bay of Bothnia. Experiments with WRF SCM are also used to determine the possible reasons behind model&amp;#8217;s biases. Preliminary results show that accurate representation of sea ice conditions, including thickness, surface temperature, albedo, and snow coverage is crucial for increasing the quality of NWP models forecasts. We emphasize the importance of further development of parametrizations focusing on the processes at the sea ice-atmosphere interface.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Wenta, M., Brus, D., Doulgeris, K., Vakkari, V., and Herman, A.: Winter atmospheric boundary layer observations over sea ice in the coastal zone of the Bay of Bothnia (Baltic Sea), Earth Syst. Sci. Data, 13, 33&amp;#8211;42, https://doi.org/10.5194/essd-13-33-2021, 2021.&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document