Influence of a Hailstreak on Boundary Layer Evolution

Severe thunderstorms developed on 20 June 1997 and produced heavy precipitation, damaging winds, and large hail over two swaths in southeastern South Dakota. Calculations of fractional vegetation coverage (scaled from 0 to 1) based upon composite satellite data indicate that, within the hailstreak region, vegetation coverage decreased from 0.50 to near 0.25 owing to the damaging effects of hail on the growing vegetation. The northern edge of the larger hailstreak was located a few kilometers south of Chamberlain, South Dakota, a National Weather Service surface observation site. Hourly observations from Chamberlain and several nearby surface sites in South Dakota are averaged over 7 days both before and after this hail event. These observations illustrate that the late-afternoon (nighttime) temperatures are 2°C higher (2°C lower) near the hailstreak after the event than before the event. Similarly, daily average dewpoint temperatures after the event are 2.6°C lower near the hailstreak. These changes are consistent with the influences of a recently devegetated zone on changes to the surface energy budget. To explore how these hailstreaks further affected the evolution of the planetary boundary layer in this region, two model simulations are performed using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5). In the control run, climatology is used for the land surface characteristics, and hence the simulation is independent of the hailstreaks. In the hailstreak simulation (HSS), the fractional vegetation coverage and soil moisture in the hailstreak regions are modified to reflect the likely conditions within the hailstreaks. Two different days are simulated: one with low surface wind speeds and one with stronger surface wind speeds. For the low surface wind speed case, the HSS simulation produces a sea-breeze-like circulation in the boundary layer by midmorning. For the stronger surface wind speed case, this sea-breeze-like circulation does not develop in the HSS, but the simulated low-level temperatures are modified over a larger area. These results suggest that to capture and reasonably simulate the evolution of boundary layer structures, there is a need for routine daily updates of land surface information. Hailstreaks also are important to consider in the future as the focus for observational studies on nonclassical mesoscale circulations.

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The Influence of Boundary Layer Processes on the Diurnal Variation of the Climatological Near-Surface Wind Speed Probability Distribution over Land*

Journal of Climate ◽

10.1175/jcli-d-11-00321.1 ◽

2012 ◽

Vol 25 (18) ◽

pp. 6441-6458 ◽

Cited By ~ 16

Author(s):

Yanping He ◽

Norman A. McFarlane ◽

Adam H. Monahan

Keyword(s):

Boundary Layer ◽

Standard Deviation ◽

Wind Speed ◽

Probability Distribution ◽

Wind Power ◽

Land Surface ◽

Vertical Structure ◽

Surface Wind ◽

Surface Wind Speed ◽

Near Surface

Abstract Knowledge of the diurnally varying land surface wind speed probability distribution is essential for surface flux estimation and wind power management. Global observations indicate that the surface wind speed probability density function (PDF) is characterized by a Weibull-like PDF during the day and a nighttime PDF with considerably greater skewness. Consideration of long-term tower observations at Cabauw, the Netherlands, indicates that this nighttime skewness is a shallow feature connected to the formation of a stably stratified nocturnal boundary layer. The observed diurnally varying vertical structure of the leading three climatological moments of near-surface wind speed (mean, standard deviation, and skewness) and the wind power density at the Cabauw site can be successfully simulated using the single-column version of the Canadian Centre for Climate Modelling and Analysis (CCCma) fourth-generation atmospheric general circulation model (CanAM4) with a new semiempirical diagnostic turbulent kinetic energy (TKE) scheme representing downgradient turbulent transfer processes for cloud-free conditions. This model also includes a simple stochastic representation of intermittent turbulence at the boundary layer inversion. It is found that the mean and the standard deviation of wind speed are most influenced by large-scale “weather” variability, while the shape of the PDF is influenced by the intermittent mixing process. This effect is quantitatively dependent on the asymptotic flux Richardson number, which determines the Prandtl number in stable flows. High vertical resolution near the land surface is also necessary for realistic simulation of the observed fine vertical structure of wind speed distribution.

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Evaluation of Global Reanalysis Land Surface Wind Speed Trends to Support Wind Energy Development Using In Situ Observations

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-20-0037.1 ◽

2021 ◽

Vol 60 (1) ◽

pp. 33-50

Author(s):

Wenxin Fan ◽

Yi Liu ◽

Adrian Chappell ◽

Li Dong ◽

Rongrong Xu ◽

...

Keyword(s):

Wind Speed ◽

Wind Energy ◽

Land Surface ◽

Turning Point ◽

Surface Wind ◽

Energy Resource ◽

Surface Wind Speed ◽

Wind Speeds ◽

Global Reanalysis

AbstractGlobal reanalysis products are important tools across disciplines to study past meteorological changes and are especially useful for wind energy resource evaluations. Studies of observed wind speed show that land surface wind speed declined globally since the 1960s (known as global terrestrial stilling) but reversed with a turning point around 2010. Whether the declining trend and the turning point have been captured by reanalysis products remains unknown so far. To fill this research gap, a systematic assessment of climatological winds and trends in five reanalysis products (ERA5, ERA-Interim, MERRA-2, JRA-55, and CFSv2) was conducted by comparing gridcell time series of 10-m wind speed with observational data from 1439 in situ meteorological stations for the period 1989–2018. Overall, ERA5 is the closest to the observations according to the evaluation of climatological winds. However, substantial discrepancies were found between observations and simulated wind speeds. No reanalysis product showed similar change to that of the global observations, although some showed regional agreement. This discrepancy between observed and reanalysis land surface wind speed indicates the need for prudence when using reanalysis products for the evaluation and prediction of winds. The possible reasons for the inconsistent wind speed trends between reanalysis products and observations are analyzed. The results show that wind energy production should select different products for different regions to minimize the discrepancy with observations.

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The Probability Distribution of Land Surface Wind Speeds

Journal of Climate ◽

10.1175/2011jcli4106.1 ◽

2011 ◽

Vol 24 (15) ◽

pp. 3892-3909 ◽

Cited By ~ 38

Author(s):

Adam H. Monahan ◽

Yanping He ◽

Norman McFarlane ◽

Aiguo Dai

Keyword(s):

Boundary Layer ◽

Weibull Distribution ◽

Land Surface ◽

Wind Shear ◽

Surface Wind ◽

Nocturnal Boundary Layer ◽

Global Network ◽

Strong Wind ◽

Wind Speeds ◽

Tropospheric Wind

Abstract The probability density function (pdf) of land surface wind speeds is characterized using a global network of observations. Daytime surface wind speeds are shown to be broadly consistent with the Weibull distribution, while nighttime surface wind speeds are generally more positively skewed than the corresponding Weibull distribution (particularly in summer). In the midlatitudes, these strongly positive skewnesses are shown to be generally associated with conditions of strong surface stability and weak lower-tropospheric wind shear. Long-term tower observations from Cabauw, the Netherlands, and Los Alamos, New Mexico, demonstrate that lower-tropospheric wind speeds become more positively skewed than the corresponding Weibull distribution only in the shallow (~50 m) nocturnal boundary layer. This skewness is associated with two populations of nighttime winds: (i) strongly stably stratified with strong wind shear and (ii) weakly stably or unstably stratified with weak wind shear. Using an idealized two-layer model of the boundary layer momentum budget, it is shown that the observed variability of the daytime and nighttime surface wind speeds can be accounted for through a stochastic representation of intermittent turbulent mixing at the nocturnal boundary layer inversion.

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Evaluation of the Ocean Surface Wind Speed Change following the Super Typhoon from Space-Borne GNSS-Reflectometry

Remote Sensing ◽

10.3390/rs12122034 ◽

2020 ◽

Vol 12 (12) ◽

pp. 2034 ◽

Cited By ~ 2

Author(s):

Hongsu Liu ◽

Shuanggen Jin ◽

Qingyun Yan

Keyword(s):

Wind Speed ◽

Correlation Coefficient ◽

Surface Wind ◽

Ocean Surface ◽

Surface Wind Speed ◽

Wind Speeds ◽

Mean Error ◽

Super Typhoon ◽

The Mean ◽

Ocean Surface Wind

Ocean surface wind speed is an essential parameter for typhoon monitoring and forecasting. However, traditional satellite and buoy observations are difficult to monitor the typhoon due to high cost and low temporal-spatial resolution. With the development of spaceborne GNSS-R technology, the cyclone global navigation satellite system (CYGNSS) with eight satellites in low-earth orbit provides an opportunity to measure the ocean surface wind speed of typhoons. Though observations are made at the extremely efficient spatial and temporal resolution, its accuracy and reliability are unclear in an actual super typhoon case. In this study, the wind speed variations over the life cycle of the 2018 Typhoon Mangkhut from CYGNSS observations were evaluated and compared with European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis-5 (ERA-5). The results show that the overall root-mean-square error (RMSE) of CYGNSS versus ECMWF was 4.12 m/s, the mean error was 1.36 m/s, and the correlation coefficient was 0.96. For wind speeds lower and greater than 15 m/s, the RMSE of CYGNSS versus ECMWF were 1.02 and 4.36 m/s, the mean errors were 0.05 and 1.61 m/s, the correlation coefficients were 0.91 and 0.90, and the average relative errors were 9.8% and 11.6%, respectively. When the typhoon reached a strong typhoon or super typhoon, the RMSE of CYGNSS with respect to ERA-5 from ECMWF was 5.07 m/s; the mean error was 3.57 m/s; the correlation coefficient was 0.52 and the average relative error was 11.0%. The CYGNSS estimation had higher precision for wind speeds below 15 m/s, but degraded when the wind speed was above 15 m/s.

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Alat Ukur Kecepatan Angin Permukaan Air Laut Berbasis Mikrokontroler

Barakuda 45: Jurnal Ilmu Perikanan dan Kelautan ◽

10.47685/barakuda45.v2i2.90 ◽

2020 ◽

Vol 2 (2) ◽

pp. 80-88

Author(s):

Waluyo Waluyo ◽

Meli Ruslinar

Keyword(s):

Wind Speed ◽

Surface Wind ◽

Surface Wind Speed ◽

Wind Data ◽

Measuring Instrument ◽

Ocean Engineering ◽

Sea Surface Wind Speed ◽

Wind Speeds ◽

Sea Surface Wind ◽

Engineering Modeling

The microcontroller is one technology that is developing so rapidly with various types and functions, one of which is Arduino Uno which can be used as a microcontroller for various functions in the field of electronics technology. This research was conducted at the Laboratory of Ocean Engineering Modeling, Marine and Fisheries Polytechnic of Karawang in March-June 2020. The purpose of this study was to create a microcontroller-based sea surface wind speed measuring instrument. Based on the results of the acquisition of wind data using a fan simulation and natural wind gusts with different wind speeds in the field show a significant tool response. The results of the comparison of data recording between the results of research with the existing wind speed measuring instrument show that there is an average tool error of 3.24%, a relative error of 3.78%, and an instrument accuracy rate of 96.76%. Thus it can be said that the ability of the tool is able to record wind data with high accuracy.

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Retrieved wind speed from the Orbiting Carbon Observatory-2

Atmospheric Measurement Techniques ◽

10.5194/amt-13-6889-2020 ◽

2020 ◽

Vol 13 (12) ◽

pp. 6889-6899

Author(s):

Robert R. Nelson ◽

Annmarie Eldering ◽

David Crisp ◽

Aronne J. Merrelli ◽

Christopher W. O'Dell

Keyword(s):

Wind Speed ◽

Near Infrared ◽

Surface Wind ◽

Surface Wind Speed ◽

Retrieval Algorithm ◽

Economic Sectors ◽

Wind Speeds ◽

Clear Sky ◽

Potential Benefits ◽

Microwave Sensors

Abstract. Satellite measurements of surface wind speed over the ocean inform a wide variety of scientific pursuits. While both active and passive microwave sensors are traditionally used to detect surface wind speed over water surfaces, measurements of reflected sunlight in the near-infrared made by the Orbiting Carbon Observatory-2 (OCO-2) are also sensitive to the wind speed. In this work, retrieved wind speeds from OCO-2 glint measurements are validated against the Advanced Microwave Scanning Radiometer-2 (AMSR2). Both sensors are in the international Afternoon Constellation (A-Train), allowing for a large number of co-located observations. Several different OCO-2 retrieval algorithm modifications are tested, with the most successful being a single-band Cox–Munk-only model. Using this, we find excellent agreement between the two sensors, with OCO-2 having a small mean bias against AMSR2 of −0.22 m s−1, an RMSD of 0.75 m s−1, and a correlation coefficient of 0.94. Although OCO-2 is restricted to clear-sky measurements, potential benefits of its higher spatial resolution relative to microwave instruments include the study of coastal wind processes, which may be able to inform certain economic sectors.

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CYGNSS Ocean Surface Wind Validation in the Tropics

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-20-0079.1 ◽

2020 ◽

Author(s):

Shakeel Asharaf ◽

Duane E. Waliser ◽

Derek J. Posselt ◽

Christopher S. Ruf ◽

Chidong Zhang ◽

...

Keyword(s):

Wind Speed ◽

Surface Wind ◽

Surface Wind Speed ◽

Satellite System ◽

Cold Pool ◽

Tropical Ocean ◽

Near Surface ◽

Wind Speeds ◽

Low Wind Speeds ◽

Global Navigation Satellite

AbstractSurface wind plays a crucial role in many local/regional weather and climate processes, especially through the exchanges of energy, mass and momentum across the Earth’s surface. However, there is a lack of consistent observations with continuous coverage over the global tropical ocean. To fill this gap, the NASA Cyclone Global Navigation Satellite System (CYGNSS) mission was launched in December 2016, consisting of a constellation of eight small spacecrafts that remotely sense near surface wind speed over the tropical and sub-tropical oceans with relatively high sampling rates both temporally and spatially. This current study uses data obtained from the Tropical Moored Buoy Arrays to quantitatively characterize and validate the CYGNSS derived winds over the tropical Indian, Pacific, and Atlantic Oceans. The validation results show that the uncertainty in CYGNSS wind speed, as compared with these tropical buoy data, is less than 2 m s-1 root mean squared difference, meeting the NASA science mission Level-1 uncertainty requirement for wind speeds below 20 m s-1. The quality of the CYGNSS wind is further assessed under different precipitation conditions, and in convective cold-pool events, identified using buoy rain and temperature data. Results show that CYGNSS winds compare fairly well with buoy observations in the presence of rain, though at low wind speeds the presence of rain appears to cause a slight positive wind speed bias in the CYGNSS data. The comparison indicates the potential utility of the CYGNSS surface wind product, which in turn may help to unravel the complexities of air-sea interaction in regions that are relatively under-sampled by other observing platforms.

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Impact of wind speeds on turbulent transport of carbon dioxide (CO2) fluxes at a tropical location in Ile - Ife, southwest Nigeria

10.5194/egusphere-egu2020-1882 ◽

2020 ◽

Author(s):

Theodora Bello ◽

Adewale Ajao ◽

Oluwagbemiga Jegede

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Land Surface ◽

Stable Boundary Layer ◽

Turbulent Transport ◽

Strong Wind ◽

Stable Boundary ◽

Wind Speeds ◽

Low Wind Speed ◽

Tropical Area

The study investigates impact of wind speeds on the turbulent transport of CO2 fluxes for a land-surface atmosphere interface in a low-wind tropical area between May 28th and June 14th, 2010; and May 24th and June 15th, 2015. Eddy covariance technique was used to acquire turbulent mass fluxes of CO2 and wind speed at the study site located inside the main campus of Obafemi Awolowo University, Ile &#8211; Ife, Nigeria. The results showed high levels of CO2 fluxes at nighttime attributed to stable boundary layer conditions and low wind speed. Large transport and distribution of CO2 fluxes were observed in the early mornings due to strong wind speeds recorded at the study location. In addition, negative CO2 fluxes were observed during the daytime attributed to prominent convective and photosynthetic activities. The study concludes there was an inverse relationship between turbulent transport of CO2 fluxes and wind speed for daytime period while nighttime CO2 fluxes showed no significant correlation.Keywords: CO2 fluxes, Wind speed, Turbulent transport, Low-wind tropical area, Stable boundary layer

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Estimation of Dissipative Heating Using Low-Level In Situ Aircraft Observations in the Hurricane Boundary Layer

Journal of the Atmospheric Sciences ◽

10.1175/2010jas3397.1 ◽

2010 ◽

Vol 67 (6) ◽

pp. 1853-1862 ◽

Cited By ~ 33

Author(s):

Jun A. Zhang

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Atmospheric Boundary Layer ◽

Surface Wind ◽

Surface Wind Speed ◽

Dissipative Heating ◽

Eddy Correlation ◽

Low Level ◽

Hurricane Boundary Layer ◽

Rate Of Dissipation

Abstract Data collected in the low-level atmospheric boundary layer in five hurricanes by NOAA research aircraft are analyzed to measure turbulence with scales small enough to retrieve the rate of dissipation. A total of 49 flux runs suitable for analysis are identified in the atmospheric boundary layer within 200 m above the sea surface. Momentum fluxes are directly determined using the eddy correlation method, and drag coefficients are also calculated. The dissipative heating is estimated using two different methods: 1) integrating the rate of dissipation in the surface layer and 2) multiplying the drag coefficient by the cube of surface wind speed. While the latter method has been widely used in theoretical models as well as several numerical models simulating hurricanes, these analyses show that using this method would significantly overestimate the magnitude of dissipative heating. Although the dataset used in this study is limited by the surface wind speed range <30 m s−1, this work highlights that it is crucial to understand the physical processes related to dissipative heating in the hurricane boundary layer for implementing it into hurricane models.

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A Comparative Assessment of Surface Wind Speed and Sea Surface Temperature over the Indian Ocean by TMI, MSMR, and ERA-40

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech2021.1 ◽

2007 ◽

Vol 24 (6) ◽

pp. 1131-1142 ◽

Cited By ~ 23

Author(s):

Anant Parekh ◽

Rashmi Sharma ◽

Abhijit Sarkar

Keyword(s):

Wind Speed ◽

Indian Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Microwave Radiometer ◽

Surface Wind ◽

Surface Wind Speed ◽

Sea Surface ◽

Wind Speeds ◽

Low Wind Speeds

A 2-yr (June 1999–June 2001) observation of ocean surface wind speed (SWS) and sea surface temperature (SST) derived from microwave radiometer measurements made by a multifrequency scanning microwave radiometer (MSMR) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) is compared with direct measurements by Indian Ocean buoys. Also, for the first time SWS and SST values of the same period obtained from 40-yr ECMWF Re-Analysis (ERA-40) have been evaluated with these buoy observations. The SWS and SST are shown to have standard deviations of 1.77 m s−1 and 0.60 K for TMI, 2.30 m s−1 and 2.0 K for MSMR, and 2.59 m s−1 and 0.68 K for ERA-40, respectively. Despite the fact that MSMR has a lower-frequency channel, larger values of bias and standard deviation (STD) are found compared to those of TMI. The performance of SST retrieval during the daytime is found to be better than that at nighttime. The analysis carried out for different seasons has raised an important question as to why one spaceborne instrument (TMI) yields retrievals with similar biases during both pre- and postmonsoon periods and the other (MSMR) yields drastically different results. The large bias at low wind speeds is believed to be due to the poorer sensitivity of microwave emissivity variations at low wind speeds. The extreme SWS case study (cyclonic condition) showed that satellite-retrieved SWS captured the trend and absolute magnitudes as reflected by in situ observations, while the model (ERA-40) failed to do so. This result has direct implications on the real-time application of satellite winds in monitoring extreme weather events.

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