scholarly journals Surface wind fields of Antarctic mesocyclones derived from ERS 1 scatterometer data

1997 ◽  
Vol 102 (D12) ◽  
pp. 13907-13921 ◽  
Author(s):  
Gareth J. Marshall ◽  
John Turner
Keyword(s):  
Surface Wind ◽  
Wind Fields

scholarly journals Impacts on wave-driven harbour agitation due to climate change in Catalan ports

2015 ◽  
Vol 15 (8) ◽  
pp. 1695-1709 ◽  
Author(s):  
J. P. Sierra ◽  
M. Casas-Prat ◽  
M. Virgili ◽  
C. Mösso ◽  
A. Sánchez-Arcilla
Keyword(s):  
Climate Change ◽  
Wind Waves ◽  
Surface Wind ◽  
Qualitative Assessment ◽  
Type Model ◽  
Slight Reduction ◽  
Wind Fields ◽  
General Applicability ◽  
Nw Mediterranean ◽  
Offshore Wave

Abstract. The objective of the present work is to analyse how changes in wave patterns due to the effect of climate change can affect harbour agitation (oscillations within the port due to wind waves). The study focuses on 13 harbours located on the Catalan coast (NW Mediterranean) using a methodology with general applicability. To obtain the patterns of agitation, a Boussinesq-type model is used, which is forced at the boundaries by present/future offshore wave conditions extracted from recently developed high-resolution wave projections in the NW Mediterranean. These wave projections were obtained with the SWAN model forced by present/future surface wind fields projected, respectively, by five different combinations of global and regional circulation models (GCMs and RCMs) for the A1B scenario. The results show a general slight reduction in the annual average agitation for most of the ports, except for the northernmost and southernmost areas of the region, where a slight increase is obtained. A seasonal analysis reveals that the tendency to decrease is accentuated in winter. However, the inter-model variability is large for both the winter and the annual analysis. Conversely, a general increase with a larger agreement among models is found during summer, which is the period with greater activity in most of the studied ports (marinas). A qualitative assessment of the factors of variability seems to indicate that the choice of GCM tends to affect the spatial pattern, whereas the choice of RCM induces a more homogeneous bias over the regional domain.

scholarly journals Interpolation framework to speed up near-surface wind simulations for data-driven wildfire applications

2018 ◽  
Vol 27 (4) ◽  
pp. 257 ◽  
Author(s):  
O. Rios ◽  
W. Jahn ◽  
E. Pastor ◽  
M. M. Valero ◽  
E. Planas
Keyword(s):  
High Resolution ◽  
Surface Wind ◽  
Computation Time ◽  
Data Driven ◽  
Wind Fields ◽  
Near Surface ◽  
Finite Set ◽  
Multiple Resolutions ◽  
Feasible Alternative ◽  
Wildfire Spread

Local wind fields that account for topographic interaction are a key element for any wildfire spread simulator. Currently available tools to generate near-surface winds with acceptable accuracy do not meet the tight time constraints required for data-driven applications. This article presents the specific problem of data-driven wildfire spread simulation (with a strategy based on using observed data to improve results), for which wind diagnostic models must be run iteratively during an optimisation loop. An interpolation framework is proposed as a feasible alternative to keep a positive lead time while minimising the loss of accuracy. The proposed methodology was compared with the WindNinja solver in eight different topographic scenarios with multiple resolutions and reference – pre-run– wind map sets. Results showed a major reduction in computation time (~100 times once the reference fields are available) with average deviations of 3% in wind speed and 3° in direction. This indicates that high-resolution wind fields can be interpolated from a finite set of base maps previously computed. Finally, wildfire spread simulations using original and interpolated maps were compared showing minimal deviations in the fire shape evolution. This methodology may have an important effect on data assimilation frameworks and probabilistic risk assessment where high-resolution wind fields must be computed for multiple weather scenarios.

Analysis of the 6 September 2015 Tornadic Storm Around the Tokyo Metropolitan Area Using Coupled 3DVAR and Incremental Analysis Updates

2017 ◽  
Vol 12 (5) ◽  
pp. 956-966
Author(s):  
Ken-ichi Shimose ◽  
◽  
Shingo Shimizu ◽  
Ryohei Kato ◽  
Koyuru Iwanami
Keyword(s):  
Real Time ◽  
Metropolitan Area ◽  
Surface Wind ◽  
Three Dimensional ◽  
Incremental Analysis ◽  
Wind Fields ◽  
Real Time Processing ◽  
Tokyo Metropolitan ◽  
Tokyo Metropolitan Area ◽  
Real Time Analysis

This study reports preliminary results from the three-dimensional variational method (3DVAR) with incremental analysis updates (IAU) of the surface wind field, which is suitable for real-time processing. In this study, 3DVAR with IAU was calculated for the case of a tornadic storm using 500-m horizontal grid spacing with updates every 10 min, for 6 h. Radial velocity observations by eight X-band multi-parameter Doppler radars and three Doppler lidars around the Tokyo Metropolitan area, Japan, were used for the analysis. In this study, three types of analyses were performed between 1800 to 2400 LST (local standard time: UTC + 9 h) 6 September 2015. The first used only 3DVAR (3DVAR), the second used 3DVAR with IAU (3DVAR+IAU), and the third analysis did not use data assimilation (CNTL). 3DVAR+IAU showed the best accuracy of the three analyses, and 3DVAR alone showed the worst accuracy, even though the background was updated every 10 min. Sharp spike signals were observed in the time series of wind speed at 10 m AGL, analyzed by 3DVAR, strongly suggesting that a “shock” was caused by dynamic imbalance due to the instantaneous addition of analysis increments to the background wind components. The spike signal was not shown in 3DVAR+IAU analysis, therefore, we suggest that the IAU method reduces the shock caused by the addition of analysis increments. This study provides useful information on the most suitable DA method for the real-time analysis of surface wind fields.

Global Scatterometer Observations of the Structure of Tropical Cyclone Wind Fields

2020 ◽  
Vol 148 (11) ◽  
pp. 4673-4692
Author(s):  
Ali Tamizi ◽  
Ian R. Young ◽  
Agustinus Ribal ◽  
Jose-Henrique Alves
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Radial Distance ◽  
Wind Fields ◽  
Forward Movement ◽  
Left Right Asymmetry ◽  
The Right ◽  
Very Large Database ◽  
Left Front ◽  
Tropical Cyclone Center

AbstractA very large database containing 24 years of scatterometer passes is analyzed to investigate the surface wind fields within tropical cyclones. The analysis confirms the left–right asymmetry of the wind field with the strongest winds directly to the right of the tropical cyclone center (Northern Hemisphere). At values greater than 2 times the radius to maximum winds, the asymmetry is approximately equal to the storm velocity of forward movement. Observed wind inflow angle (i.e., storm motion not subtracted) is shown to vary both radially and azimuthally within the tropical cyclone. The smallest observed wind inflow angles are found in the left-front quadrant with the largest values in the right-rear quadrant. As the velocity of forward movement increases and the central pressure decreases, observed inflow angles ahead of the storm decrease and those behind the storm increase. In the right-rear quadrant, the observed inflow angle increases with radius from the storm center. In all other quadrants, the observed inflow angle is approximately constant as a function of radial distance.

Tropical Cyclone Inner-Core Kinetic Energy Evolution

2008 ◽  
Vol 136 (12) ◽  
pp. 4882-4898 ◽  
Author(s):  
Katherine S. Maclay ◽  
Mark DeMaria ◽  
Thomas H. Vonder Haar
Keyword(s):  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Inner Core ◽  
Surface Wind ◽  
Statistical Testing ◽  
Vertical Shear ◽  
Structure Evolution ◽  
Wind Fields ◽  
Secondary Eyewall Formation ◽  
Wind Structure

Abstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind field. To gain a better understanding of wind structure evolution, TC 0–200-km wind fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change and, for convenience, are referred to as measurements of storm size [storms with greater (less) KE for their given intensity are considered large (small)]. It is established that TCs generally either intensify and do not grow or they weaken/maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus nongrowing storms in each intensification regime. Results suggest two primary types of growth processes: (i) secondary eyewall formation and eyewall replacement cycles, an internally dominated process, and (ii) external forcing from the synoptic environment. One of the most significant environmental forcings is the vertical shear. Under light shear, TCs intensify but do not grow; under moderate shear, they intensify less but grow more; under very high shear, they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir–Simpson hurricane scale.

scholarly journals Development and Testing of Tropical Cyclone Parametric Wind Models Tailored for Midlatitude Application—Preliminary Results

2006 ◽  
Vol 45 (9) ◽  
pp. 1244-1260 ◽  
Author(s):  
Allan W. MacAfee ◽  
Garry M. Pearson
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Angular Size ◽  
Absolute Error ◽  
Parametric Models ◽  
Wind Fields ◽  
Low Latitude ◽  
New Techniques ◽  
Qualitative And Quantitative ◽  
Using Data

Abstract Over the years, researchers have developed parametric wind models to depict the surface winds within a tropical cyclone (TC). Most models were developed using data from aircraft flights into low-latitude (south of 30°N) TCs in the Atlantic Ocean, Gulf of Mexico, and Caribbean Sea. Such models may not adequately reproduce the midlatitude TC wind field where synoptic interaction and acceleration are more pronounced. To tailor these models for midlatitude application, latitude-dependent angular size and shape details were added by using new techniques to set values for model input parameters and by incorporating additional field-shaping procedures. A method to assess the different techniques and field-shaping procedures was developed in which qualitative and quantitative assessment was performed using five parametric models and samples of buoy and 2D surface wind data. Contingency tables and statistical scores such as mean absolute error and bias were used to select the techniques and procedures that create the most realistic depiction of low- and midlatitude TC surface wind fields.

scholarly journals Statistical Downscaling of Gridded Wind Speed Data Using Local Topography

2017 ◽  
Vol 18 (2) ◽  
pp. 335-348 ◽  
Author(s):  
Adam Winstral ◽  
Tobias Jonas ◽  
Nora Helbig
Keyword(s):  
Wind Speed ◽  
Statistical Downscaling ◽  
Surface Wind ◽  
Horizontal Resolution ◽  
Wind Data ◽  
Wind Fields ◽  
Forecast Performance ◽  
Wind Speeds ◽  
Mountain Environments ◽  
High Winds

Abstract Winds, particularly high winds, strongly affect snowmelt and snow redistribution. High winds during rain-on-snow events can lead to catastrophic flooding while strong redistribution events in mountain environments can generate dangerous avalanche conditions. To provide adequate warnings, accurate wind data are required. Yet, mountain wind fields exhibit a high degree of heterogeneity at small spatial lengths that are not resolved by currently available gridded forecast data. Wind data from over 200 stations across Switzerland were used to evaluate two forecast surface wind products (~2- and 7-km horizontal resolution) and develop a statistical downscaling technique to capture these finer-scaled heterogeneities. Wind exposure metrics derived from a 25-m horizontal resolution digital elevation model effectively segregated high, moderate, and low wind speed sites. Forecast performance was markedly compromised and biased low at the exposed sites and biased high at the sheltered, valley sites. It was also found that the variability of predicted wind speeds at these sites did not accurately represent the observed variability. A novel optimization scheme that accounted for local terrain structure while also nudging the forecasted distributions to better match the observed distributions and variability was developed. The resultant statistical downscaling technique notably decreased biases across a range of elevations and exposures and provided a better match to observed wind speed distributions.

scholarly journals Comparison of regional and global reanalysis near-surface winds with station observations over Germany

2015 ◽  
Vol 12 (1) ◽  
pp. 187-198 ◽  
Author(s):  
A. K. Kaiser-Weiss ◽  
F. Kaspar ◽  
V. Heene ◽  
M. Borsche ◽  
D. G. H. Tan ◽  
...  
Keyword(s):  
Information Source ◽  
Surface Wind ◽  
Wind Fields ◽  
Near Surface ◽  
Wind Speeds ◽  
Energy Applications ◽  
The North ◽  
Independent Observations ◽  
Spatio Temporal ◽  
The North Atlantic Oscillation

Abstract. Reanalysis near-surface wind fields from multiple reanalyses are potentially an important information source for wind energy applications. Inter-comparing reanalyses via employing independent observations can help to guide users to useful spatio-temporal scales. Here we compare the statistical properties of wind speeds observed at 210 traditional meteorological stations over Germany with the reanalyses' near-surface fields, confining the analysis to the recent years (2007 to 2010). In this period, the station time series in Germany can be expected to be mostly homogeneous. We compare with a regional reanalysis (COSMO-REA6) and two global reanalyses, ERA-Interim and ERA-20C. We show that for the majority of the stations, the Weibull parameters of the daily mean wind speed frequency distribution match remarkably well with the ones derived from the reanalysis fields. High correlations (larger than 0.9) can be found between stations and reanalysis monthly mean wind speeds all over Germany. Generally, the correlation between the higher resolved COSMO-REA6 wind fields and station observations is highest, for both assimilated and non-assimilated (i.e., independent) observations. As expected from the lower spatial resolution and reduced amount of data assimilated into ERA-20C, the correlation of monthly means decreases somewhat relative to the other reanalyses (in our investigated period of 2007 to 2010). Still, the inter-annual variability connected to the North Atlantic Oscillation (NAO) found in the reanalysis surface wind anomalies is in accordance with the anomalies recorded by the stations. We discuss some typical examples where differences are found, e.g., where the mean wind distributions differ (probably related to either height or model topography differences) and where the correlations break down (because of unresolved local topography) which applies to a minority of stations. We also identified stations with homogeneity problems in the reported station values, demonstrating how reanalyses can be applied to support quality control for the observed station data. Finally, as a demonstration of concept, we discuss how comparing feedback files of the different reanalyses can guide users to useful scales of variability.

scholarly journals Preliminary Analysis of Wind Retrieval Based on GF-3 Wave Mode Images

2018 ◽  
Author(s):  
Lei Wang ◽  
Bing Han ◽  
Xinzhe Yuan ◽  
Bin Lei ◽  
Chibiao Ding ◽  
...  
Keyword(s):  
Wind Speed ◽  
Incidence Angle ◽  
Surface Wind ◽  
Wave Mode ◽  
Azimuth Angle ◽  
Calibration Constant ◽  
Wind Fields ◽  
Wind Retrieval ◽  
Geophysical Model ◽  
The Cross

In this paper, we analyze the measurements of the normalized radar cross-section(NRCS) in Wave Mode for Chinese C-band Gaofen-3(GF-3) synthetic aperture radar (SAR). Based on 2779 images from GF-3 quad-polarization SAR in Wave Mode and collocated wind vectors from ERA-Interim, we verify the feasibility of using ocean surface wind fields and VV-polarized NRCS to perform normalized calibration. The method uses well-validated empirical C-band geophysical model function (CMOD4) to estimate the calibration constant for each beam. The Amazon rainforest experiment results show that the accuracy of obtained calibration constant meets the requirements. In addition, the relationship between cross-pol NRCS and wind vectors is discussed. The cross-pol NRCS increases linearly with wind speed and it has an approximate cosine modulation with the wind direction when the wind speed is greater than 8m/s. The cross-polarized system noise floor is low enough to ignore it in wind retrieval. Furthermore, we also investigate the properties of the polarization ratio, denoted PR, and show that it is dependent on incidence angle and azimuth angle. Two empirical models of the PR are fitted, one as a function of incidence angle only, the other with additional dependence on azimuth angle. Assessments show that the σ_VV^0 retrieved from new PR models as well as σ_HH^0 is in good agreement with σ_VV^0 extracted from SAR images directly. And it is also shown that considering the azimuth angle can improve polarization conversion accuracy.

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