Can Polar Lows be Objectively Identified and Tracked in the ECMWF Operational Analysis and the ERA-Interim Reanalysis?

Abstract Polar lows are maritime mesocyclones associated with intense surface wind speeds and oceanic heat fluxes at high latitudes. The ability of the Interim ECMWF Re-Analysis (ERA-Interim, hereafter ERAI) to represent polar lows in the North Atlantic is assessed by comparing ERAI and the ECMWF operational analysis for the period 2008–11. First, the representation of a set of satellite-observed polar lows over the Norwegian and Barents Seas in the operational analysis and ERAI is analyzed. Then, the possibility of directly identifying and tracking the polar lows in the operational analysis and ERAI is explored using a tracking algorithm based on 850-hPa vorticity with objective identification criteria on cyclone dynamical intensity and atmospheric static stability. All but one of the satellite-observed polar lows with a lifetime of at least 6 h have an 850-hPa vorticity signature of a collocated mesocyclone in both the operational analysis and ERAI for most of their life cycles. However, the operational analysis has vorticity structures that better resemble the observed cloud patterns and stronger surface wind speed intensities compared to those in ERAI. By applying the objective identification criteria, about 55% of the satellite-observed polar lows are identified and tracked in ERAI, while this fraction increases to about 70% in the operational analysis. Particularly in ERAI, the remaining observed polar lows are mainly not identified because they have too weak wind speed and vorticity intensity compared to the tested criteria. The implication of the tendency of ERAI to underestimate the polar low dynamical intensity for future studies of polar lows is discussed.

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Stilling and Recovery of the Surface Wind Speed Based on Observation, Reanalysis, and Geostrophic Wind Theory over China from 1960 to 2017

Journal of Climate ◽

10.1175/jcli-d-19-0281.1 ◽

2020 ◽

Vol 33 (10) ◽

pp. 3989-4008 ◽

Cited By ~ 1

Author(s):

Zhengtai Zhang ◽

Kaicun Wang

Keyword(s):

Wind Speed ◽

Decadal Variability ◽

Surface Wind ◽

Geostrophic Wind ◽

Surface Wind Speed ◽

Strong Wind ◽

Wind Speeds ◽

The North ◽

Wind Theory ◽

Weak Winds

AbstractSurface wind speed (SWS) from meteorological observation, global atmospheric reanalysis, and geostrophic wind speed (GWS) calculated from surface pressure were used to study the stilling and recovery of SWS over China from 1960 to 2017. China experienced anemometer changes and automatic observation transitions in approximately 1969 and 2004, resulting in SWS inhomogeneity. Therefore, we divided the entire period into three sections to study the SWS trend, and found a near-zero annual trend in the SWS in China from 1960 to 1969, a significant decrease of −0.24 m s−1 decade−1 from 1970 to 2004, and a weak recovery from 2005 to 2017. By defining the 95th and 5th percentiles of daily mean wind speeds as strong and weak winds, respectively, we found that the SWS decrease was primarily caused by a strong wind decrease of −8% decade−1 from 1960 to 2017, but weak wind showed an insignificant decreasing trend of −2% decade−1. GWS decreased with a significant trend of −3% decade−1 before the 1990s; during the 1990s, GWS increased with a trend of 3% decade−1 whereas SWS continued to decrease with a trend of 10% decade−1. Consistent with SWS, GWS demonstrated a weak increase after the 2000s. After detrending, both SWS and GWS showed synchronous decadal variability, which is related to the intensity of Aleutian low pressure over the North Pacific. However, current reanalyses cannot reproduce the decadal variability and cannot capture the decreasing trend of SWS either.

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Stilling and Recovery of the Surface Wind Speed Based on Observation, Reanalysis, and Geostrophic Wind Theory over China from 1960 to 2017

10.5194/egusphere-egu2020-2501 ◽

2020 ◽

Author(s):

Zhengtai Zhang ◽

Kaicun Wang

Keyword(s):

Wind Speed ◽

Decadal Variability ◽

Surface Wind ◽

Geostrophic Wind ◽

Surface Wind Speed ◽

Strong Wind ◽

Wind Speeds ◽

The North ◽

Wind Theory ◽

Weak Winds

Surface wind speed (SWS) from meteorological observation, global atmospheric reanalysis, and geostrophic wind speed (GWS) calculated from surface pressure were used to study the stilling and recovery of SWS over China from 1960 to 2017. China experienced anemometer changes and automatic observation transitions in approximately 1969 and 2004, resulting in SWS inhomogeneity. Therefore, we divided the entire period into three sections to study the SWS trend, and found a near zero annual trend in the SWS in China from 1960 to 1969, a significant decrease of -0.24 m/s decade-1 from 1970 to 2004, and a weak recovery from 2005 to 2017. By defining the 95th and 5th percentiles of monthly mean wind speeds as strong and weak winds, respectively, we found that the SWS decrease was primarily caused by a strong wind decrease of -8 % decade-1 from 1960 to 2017, but weak wind showed an insignificant decreasing trend of -2 % decade-1. GWS decreased with a significant trend of -3 % decade-1 before the 1990s, during the 1990s, GWS increased with a trend of 3 % decade-1 whereas SWS continued to decrease with a trend of 10 % decade-1. Consistent with SWS, GWS demonstrated a weak increase after the 2000s. After detrended, both of SWS and GWS showed synchronous decadal variability, which is related to the intensity of Aleutian low pressure over the North Pacific. However, current reanalyses cannot reproduce the decadal variability, and can not capture the decreasing trend of SWS either.

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Estimating a relationship between aerosol optical thickness and surface wind speed over the ocean

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-11621-2006 ◽

2006 ◽

Vol 6 (6) ◽

pp. 11621-11651 ◽

Cited By ~ 4

Author(s):

P. Glantz ◽

D. E. Nilsson ◽

W. von Hoyningen-Huene

Keyword(s):

Wind Speed ◽

Optical Thickness ◽

Surface Wind ◽

Surface Wind Speed ◽

Sea Salt ◽

Aerosol Optical Thickness ◽

Marine Aerosols ◽

Hygroscopic Growth ◽

The North ◽

The North Pacific

Abstract. Retrieved aerosol optical thickness (AOT) based on data obtained by the Sea viewing Wide Field Sensor (SeaWiFS) is combined with surface wind speed, obtained at the European Centre for Medium-Range Weather Forecasts (ECMWFs), over the North Pacific for September 2001. In this study a cloud screening approach is introduced in an attempt to exclude pixels partly or fully covered by clouds. The relatively broad swath width for which the nadir looking SeaWiFS instrument scanned over the North Pacific means that the AOT can be estimated according to relatively large range of wind speeds for each of the scenes analyzed. The sensitivity in AOT due to sea salt and hygroscopic growth of the marine aerosols has also been investigated. The validation of the results is based on previous parameterization in combination with the environmental quantities wind speed, RH and boundary layer height (BLH), estimated at the ECMWF. In this study a factor of 2 higher mean AOT is obtained for a wind speed up to about 13 m s−1 for September 2001 over remote ocean areas. Furthermore, a factor of 2 higher AOT is more or less supported by the validation of the results. Approximately, 50% of the enhancement seems to be due to hygroscopic growth of the marine aerosols and the remaining part due to increase in the sea salt particle mass concentrations, caused by a wind driven water vapor and sea salt flux, respectively. Reasonable agreement occurs also between satellites retrieved aerosol optical thickness and AOT observed at several AERONET (Aerosol Robotic NETwork) ground-based remote sensing stations. Finally, possible reasons why relatively large standard deviations occur around the mean values of AOT estimated for a single scene are discussed.

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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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Comparing Polar Lows in Atmospheric Reanalyses: Arctic System Reanalysis versus ERA-Interim

Monthly Weather Review ◽

10.1175/mwr-d-16-0333.1 ◽

2017 ◽

Vol 145 (6) ◽

pp. 2375-2383 ◽

Cited By ~ 12

Author(s):

Julia Smirnova ◽

Pavel Golubkin

Keyword(s):

Strong Dependence ◽

Surface Wind ◽

Surface Wind Speed ◽

Static Stability ◽

Relative Vorticity ◽

Reference List ◽

Near Surface ◽

Polar Lows ◽

Polar Low ◽

Definition Of

Abstract Representation of polar lows in the new high-resolution Arctic System Reanalysis (ASR) was for the first time assessed and compared to that in the ERA-Interim. Substantial improvements were found in the 850-hPa relative vorticity and near-surface wind speed information. The latter was found to be in close agreement with satellite-derived estimates. Representation of polar lows from a widely used selective list in ERA-Interim and ASR was estimated as 48% and 89%, respectively. The proportion of polar lows represented in ASR is substantially higher than reported for other reanalyses in previous studies. Verifications were found to be sensitive to the polar low reference list used, and to the definition of a polar low. As found, when a more complete polar low list from a recent satellite-derived climatology was used, the proportion of represented events decreased to 26% and 66% for ERA-Interim and ASR, respectively. Variations in polar low representation in reanalyses were also observed in different regions, with the highest proportion resolved in the Norwegian Sea. Strong dependence between polar low sizes and their representation in ERA-Interim was found. In the case of ASR, polar low representation remains constant in the size range of 200–500 km and slightly decreases only for the smallest systems with diameters less than 200 km. Usage of the strict threshold of 43 K for the atmospheric static stability criterion was found to exclude a considerable number of otherwise well-represented polar lows.

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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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Wind Speed, Surface Flux, and Convection Coupling from CYGNSS Data

10.5194/egusphere-egu21-12855 ◽

2021 ◽

Author(s):

Eric Maloney ◽

Hien Bui ◽

Emily Riley Dellaripa ◽

Bohar Singh

Keyword(s):

Heat Flux ◽

Wind Speed ◽

Latent Heat ◽

Latent Heat Flux ◽

Surface Wind ◽

Surface Flux ◽

Surface Wind Speed ◽

Surface Fluxes ◽

Heat Fluxes ◽

Boreal Summer

This study analyzes wind speed and surface latent heat flux anomalies from the Cyclone Global Navigation Satellite System (CYGNSS), aiming to understand the physical mechanisms regulating intraseasonal convection, particularly associated with the Madden-Julian oscillation (MJO). The importance of wind-driven surface flux variability for supporting east Pacific diurnal convective disturbances during boreal summer is also examined. An advantage of CYGNSS compared to other space-based datasets is that its surface wind speed retrievals have reduced attenuation by precipitation, thus providing improved information about the importance of wind-induced surface fluxes for the maintenance of convection. Consistent with previous studies from buoys, CYGNSS shows that enhanced MJO precipitation is associated with enhanced wind speeds, and that associated surface heat fluxes anomalies have a magnitude about 7%-12% of precipitation anomalies. Thus, latent heat flux anomalies are an important maintenance mechanism for MJO convection through the column moist static energy budget. A composite analysis during boreal summer over the eastern north Pacific also supports the idea that wind-induced surface flux is important for MJO maintenance there. We also show the surface fluxes help moisten the atmosphere in advance of diurnal convective disturbances that propagate offshore from the Colombian Coast during boreal summer, helping to sustain such convection. &#160;

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Evaluation of Extratropical Cyclone Precipitation in the North Atlantic Basin: An Analysis of ERA-Interim, WRF, and Two CMIP5 Models

Journal of Climate ◽

10.1175/jcli-d-17-0308.1 ◽

2018 ◽

Vol 31 (6) ◽

pp. 2345-2360 ◽

Cited By ~ 17

Author(s):

James F. Booth ◽

Catherine M. Naud ◽

Jeff Willison

Keyword(s):

Wind Speed ◽

North Atlantic ◽

Surface Wind ◽

Wrf Model ◽

Surface Wind Speed ◽

Convective Precipitation ◽

Cmip5 Models ◽

Convection Scheme ◽

The North ◽

The North Atlantic

The representation of extratropical cyclone (ETC) precipitation in general circulation models (GCMs) and the Weather Research and Forecasting (WRF) Model is analyzed. This work considers the link between ETC precipitation and dynamical strength and tests if parameterized convection affects this link for ETCs in the North Atlantic basin. Lagrangian cyclone tracks of ETCs in ERA-Interim (ERAI), GISS and GFDL CMIP5 models, and WRF with two horizontal resolutions are utilized in a compositing analysis. The 20-km-resolution WRF Model generates stronger ETCs based on surface wind speed and cyclone precipitation. The GCMs and ERAI generate similar composite means and distributions for cyclone precipitation rates, but GCMs generate weaker cyclone surface winds than ERAI. The amount of cyclone precipitation generated by the convection scheme differs significantly across the datasets, with the GISS model generating the most, followed by ERAI and then the GFDL model. The models and reanalysis generate relatively more parameterized convective precipitation when the total cyclone-averaged precipitation is smaller. This is partially due to the contribution of parameterized convective precipitation occurring more often late in the ETC’s life cycle. For reanalysis and models, precipitation increases with both cyclone moisture and surface wind speed, and this is true if the contribution from the parameterized convection scheme is larger or not. This work shows that these different models generate similar total ETC precipitation despite large differences in the parameterized convection, and these differences do not cause unexpected behavior in ETC precipitation sensitivity to cyclone moisture or surface wind speed.

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