scholarly journals Assimilation of DAWN Doppler Wind Lidar Data During the 2017 Convective Processes Experiment (CPEX): Impact on the Precipitation and Flow Structure

2020 ◽  
Author(s):  
Svetla Hristova-Veleva ◽  
Sara Q. Zhang ◽  
F. Joseph Turk ◽  
Ziad S. Haddad ◽  
Randy C. Sawaya
Keyword(s):  
Weather Forecasting ◽  
Convective Precipitation ◽  
Cold Pool ◽  
Near Surface ◽  
Convective Processes ◽  
Precipitation Structure ◽  
Wind Lidar ◽  
Individual Variables ◽  
The Impact ◽  
Doppler Wind Lidar

Abstract. An improved representation of the 3-D air motion and precipitation structure through forecast models and assimilation of observations is vital for improvements in weather forecasting capabilities. However, there is little independent data to properly validate a model forecast of precipitation structure when the underlying dynamics are evolving on short convective times scales. Using data from the JPL Ku/Ka-band Airborne Precipitation Radar (APR-2) and the 2-um Doppler Aerosol Wind (DAWN) lidar collected during the 2017 Convective Processes Experiment (CPEX), the NASA Unified Weather Research and Forecasting (WRF) Ensemble Data Assimilation System (EDAS) modeling system was used to quantify the impact of the high resolution, sparsely-sampled DAWN measurements on the analyzed variables and on the forecast when the DAWN winds were assimilated. Overall, the assimilation of the DAWN wind profiles had a discernible impact to the wind field and the evolution and timing of the 3-D precipitation structure. Analysis of individual variables revealed that the assimilation of the DAWN winds resulted in important and coherent modifications of the environment. It led to increase of the near surface convergence, temperature and water vapor, creating more favorable conditions for the development of convection exactly where it was observed (but not present in the control run). Comparison to APR-2 and observations by the Global Precipitation Measurement (GPM) satellite shows a much-improved forecast after the assimilation of the DAWN winds – development of precipitation where there was none, more organized precipitation where there was some, and a much more intense and organized cold pool, similar to the analysis of the dropsonde data. Onset of the vertical evolution of the precipitation showed similar radar-derived cloud top heights, but delayed in time. While this investigation was limited to a single CPEX flight date, the investigation design is appropriate for further investigation of the impact of airborne Doppler wind lidar observations upon short-term convective precipitation forecasts.

scholarly journals Relationship between wind observation accuracy and the ascending node of the sun-synchronous orbit for the Aeolus-type spaceborne Doppler wind lidar

2021 ◽  
Vol 14 (7) ◽  
pp. 4787-4803
Author(s):  
Chuanliang Zhang ◽  
Xuejin Sun ◽  
Wen Lu ◽  
Yingni Shi ◽  
Naiying Dou ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Pulse Energy ◽  
Laser Pulse Energy ◽  
Background Radiation ◽  
The Sun ◽  
Wind Observation ◽  
Rayleigh Channel ◽  
Wind Lidar ◽  
The Impact ◽  
Doppler Wind Lidar

Abstract. The launch and operation of the first spaceborne Doppler wind lidar (DWL), Aeolus, is of great significance for observing the global wind field. Aeolus operates on a sun-synchronous dawn–dusk orbit to minimize the negative impact of solar background radiation (SBR) on wind observation accuracy. Future spaceborne DWLs may not operate on sun-synchronous dawn–dusk orbits due to their observational purposes. The impact of the local time of ascending node (LTAN) crossing of sun-synchronous orbits on the wind observation accuracy was studied in this paper by proposing two given Aeolus-type spaceborne DWLs operating on the sun-synchronous orbits with LTANs of 15:00 and 12:00 LT. On these two new orbits, the increments of the averaged SBR received by the new spaceborne DWLs range from 39 to 56 mW m−2 sr−1 nm−1 under cloud-free skies near the summer and winter solstices, which will lead to uncertainties of 0.19 and 0.27 m s−1 in the increment of the averaged Rayleigh channel wind observations for 15:00 and 12:00 LT orbits using the instrument parameters of Aeolus with 30 measurements per observation and 20 laser pulses per measurement. This demonstrates that Aeolus operating on the sun-synchronous dawn–dusk orbit is the optimal observation scenario, and the random error caused by the SBR will be larger on other sun-synchronous orbits. Increasing the laser pulse energy of the new spaceborne DWLs is used to lower the wind observation uncertainties, and a method to quantitatively design the laser pulse energy according to the specific accuracy requirements is proposed in this study based on the relationship between the signal-to-noise ratio and the uncertainty of the response function of the Rayleigh channel. The laser pulse energies of the two new spaceborne DWLs should be set to 70 mJ based on the statistical results obtained using the method. The other instrument parameters should be the same as those of Aeolus. Based on the proposed parameters, the accuracies of about 77.19 % and 74.71 % of the bins of the two new spaceborne DWLs would meet the accuracy requirements of the European Space Agency (ESA) for Aeolus. These values are very close to the 76.46 % accuracy of an Aeolus-type spaceborne DWL when it is free of the impact of the SBR. Moreover, the averaged uncertainties of the two new spaceborne DWLs are 2.62 and 2.69 m s−1, which perform better than that of Aeolus (2.77 m s−1).

scholarly journals Improved methane emission estimates using AVIRIS-NG and an Airborne Doppler Wind Lidar

2021 ◽  
Author(s):  
Andrew Thorpe ◽  
Christopher O’Handley ◽  
George Emmitt ◽  
Philip Decola ◽  
Francesca Hopkins ◽  
...  
Keyword(s):  
Wind Speed ◽  
Emission Rate ◽  
Sonic Anemometer ◽  
Surface Measurement ◽  
Emission Rates ◽  
Ch4 Emission ◽  
Near Surface ◽  
Wind Measurements ◽  
Wind Lidar ◽  
Doppler Wind Lidar

<p>This study demonstrates the utility of combining Airborne Doppler Wind Lidar measurements and quantitative methane (CH4) retrievals from the Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) to estimate CH4 emission rates. In a controlled release experiment, Twin Otter Doppler Wind Lidar (TODWL) observed wind speed and direction agreed closely with sonic anemometer measurements and CH4 emission rates derived from TODWL observations were more accurate than those using the sonic during periods of stable winds. During periods exhibiting rapid shifts in wind speed and direction, estimating emission rates proved more challenging irrespective of the use of model, sonic, or TODWL wind data. Overall, TODWL was able to provide accurate wind measurements and emission rate estimates despite the variable wind conditions and excessive flight level turbulence which impacted near surface measurement density. TODWL observed winds were also used to constrain CH4 emissions at a refinery, landfill, wastewater facility, and dairy digester. At these sites, TODWL wind measurements agreed well with wind observations from nearby meteorological stations, and when combined with quantitative CH4 plume imagery, yielded emission rate estimates that were similar to those obtained using model winds.</p>

scholarly journals Impact of Lidar Data Assimilation on Low-Level Wind Shear Simulation at Lanzhou Zhongchuan International Airport, China: A Case Study

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1342
Author(s):  
Lanqian Li ◽  
Ningjing Xie ◽  
Longyan Fu ◽  
Kaijun Zhang ◽  
Aimei Shao ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Wind Shear ◽  
Three Dimensional ◽  
Wrf Model ◽  
Lidar Data ◽  
Positive Role ◽  
Low Level ◽  
Wind Lidar ◽  
The Impact ◽  
Doppler Wind Lidar

Doppler wind lidar has played an important role in alerting low-level wind shear (LLW). However, these high-resolution observations are underused in the model-based analysis and forecasting of LLW. In this regard, we employed the Weather Research and Forecasting (WRF) model and its three-dimensional variational (3D-VAR) system to investigate the impact of lidar data assimilation (DA) on LLW simulations. Eight experiments (including six assimilation experiments) were designed for an LLW process as reported by pilots, in which different assimilation intervals, assimilation timespans, and model vertical resolutions were examined. Verified against observations from Doppler wind lidar and an automated weather observing system (AWOS), the introduction of lidar data is helpful for describing the LLW event, which can represent the temporal and spatial features of LLW, whereas experiments without lidar DA have no ability to capture LLW. While lidar DA has an obviously positive role in simulating LLW in the 10–20 min after the assimilation time, this advantage cannot be maintained over a longer time. Therefore, a smaller assimilation interval is favorable for improving the simulated effect of LLW. In addition, increasing the vertical resolution does not evidently improve the experimental results, either with or without assimilation.

scholarly journals Contributions of Surface Sensible Heat Fluxes to Tropical Cyclone. Part I: Evolution of Tropical Cyclone Intensity and Structure

2015 ◽  
Vol 72 (1) ◽  
pp. 120-140 ◽  
Author(s):  
Zhanhong Ma ◽  
Jianfang Fei ◽  
Xiaogang Huang ◽  
Xiaoping Cheng
Keyword(s):  
Tropical Cyclone ◽  
Convective Available Potential Energy ◽  
Potential Temperature ◽  
Great Sensitivity ◽  
Heat Fluxes ◽  
Cold Pool ◽  
Sensible Heat ◽  
Near Surface ◽  
Budget Analysis ◽  
The Impact

Abstract The contributions of surface sensible heat fluxes (SHX) to the evolution of tropical cyclone (TC) intensity and structure are examined in this study by conducting cloud-resolving simulations. Results suggest that although the peak values of SHX could account for nearly 30% of those of the total surface latent and sensible heat fluxes, the impact of SHX on TC intensification is nonetheless not distinct. However, the TC size shows great sensitivity to the SHX that the storm is shrunk by over 20% after removing the SHX. A potential temperature budget analysis indicates that the adiabatic cooling accompanying the radial inflow is largely balanced by the transfer of sensible heat fluxes rather than the entrainment of subsiding air from aloft. If there is upward transfer of SHX from underlying ocean so that the near-surface potential temperature decreases upward, the SHX will play a vital role; instead, if the upward SHX are absent so that the potential temperature increases upward near the surface, the downward sensible heat fluxes become the dominant contributor to warm the inflow air. The changes in TC size are found to be primarily caused by the rainband activities. The SHX help maintain high convective available potential energy as well as the cold pool feature outside the eyewall, thus being crucial for the growth of outer rainbands. If without upward transport of SHX, the outer-rainband activities could be largely suppressed, thereby leading to a decrease of the TC size.

The impact of atmospheric stratification on a space-borne Doppler wind lidar

1998 ◽  
Vol 45 (8) ◽  
pp. 1583-1599 ◽  
Author(s):  
J. M. Vaughan ◽  
D. W. Brown ◽  
D. V. Willetts
Keyword(s):  
Atmospheric Stratification ◽  
Wind Lidar ◽  
The Impact ◽  
Doppler Wind Lidar

scholarly journals A Numerical Sensitivity Study on the Impact of Soil Moisture on Convection-Related Parameters and Convective Precipitation over Complex Terrain

2011 ◽  
Vol 68 (12) ◽  
pp. 2971-2987 ◽  
Author(s):  
Christian Barthlott ◽  
Norbert Kalthoff
Keyword(s):  
Soil Moisture ◽  
Complex Terrain ◽  
Weather Prediction ◽  
Sensitivity Study ◽  
Convective Precipitation ◽  
Small Scale ◽  
Near Surface ◽  
Initial Soil Moisture ◽  
Initial Soil ◽  
The Impact

Abstract The impact of soil moisture on convection-related parameters and convective precipitation over complex terrain is studied by numerical experiments using the nonhydrostatic Consortium for Small-Scale Modeling (COSMO) model. For 1 day of the Convective and Orographically Induced Precipitation Study (COPS) conducted during summer 2007 in southwestern Germany and eastern France, initial soil moisture is varied from −50% to +50% of the reference run in steps of 5%. As synoptic-scale forcing is weak on the day under investigation, the triggering of convection is mainly due to soil–atmosphere interactions and boundary layer processes. Whereas a systematic relationship to soil moisture exists for a number of variables (e.g., latent and sensible fluxes at the ground, near-surface temperature, and humidity), a systematic increase of 24-h accumulated precipitation with increasing initial soil moisture is only present in the simulations that are drier than the reference run. The time evolution of convective precipitation can be divided into two regimes with different conditions to initiate and foster convection. Furthermore, the impact of soil moisture is different for the initiation and modification of convective precipitation. The results demonstrate the high sensitivity of numerical weather prediction to initial soil moisture fields.

scholarly journals Influences on Observed Near-Surface Gust Factors in Landfalling U.S. Gulf Coast Hurricanes: 2004–08

2016 ◽  
Vol 55 (12) ◽  
pp. 2587-2611 ◽  
Author(s):  
Ian M. Giammanco ◽  
John L. Schroeder ◽  
Forrest J. Masters ◽  
Peter J. Vickery ◽  
Richard J. Krupar ◽  
...  
Keyword(s):  
Gulf Coast ◽  
Surface Wind ◽  
Monitoring Program ◽  
Flow Characteristics ◽  
The United States ◽  
Convective Precipitation ◽  
Wind Flow ◽  
Near Surface ◽  
Precipitation Structure ◽  
Gust Factors

AbstractThe deployment of ruggedized surface observing platforms by university research programs in the path of landfalling tropical cyclones has yielded a wealth of information regarding the near-surface wind flow characteristics. Data records collected by Texas Tech University’s Wind Engineering Mobile Instrument Tower Experiment and StickNet probes and by the Florida Coastal Monitoring Program along the Gulf Coast of the United States from 2004 to 2008 were compiled to examine influences on near-surface gust factors. Archived composite reflectivity data from coastal WSR-88D instruments were also merged with the tower records to investigate the influence of precipitation structure. Wind records were partitioned into 10-min segments, and the ratio of the peak moving-average 3-s-gust wind speed to the segment mean was used to define a gust factor. Observations were objectively stratified into terrain exposure categories to determine if factors beyond those associated with surface frictional effects can be extracted from the observations. Wind flow characteristics within exposure classes were weakly influenced by storm-relative position and precipitation structure. Eyewall observations showed little difference in mean gust factors when compared with other regions. In convective precipitation, only peak gust factors were slightly larger than those found in stratiform conditions, with little differences in the mean. Gust factors decreased slightly with decreasing radial distance in rougher terrain exposures and did not respond to radar-observed changes in precipitation structure. In two limited comparisons, near-surface gusts did not exceed the magnitude of the wind maximum aloft detected through wind profiles that were derived from WSR-88D velocity–azimuth displays.

scholarly journals Joint analysis of convective structure from the APR-2 precipitation radar and the DAWN Doppler wind lidar during the 2017 Convective Processes Experiment (CPEX)

2020 ◽  
Vol 13 (8) ◽  
pp. 4521-4537 ◽  
Author(s):  
F. Joseph Turk ◽  
Svetla Hristova-Veleva ◽  
Stephen L. Durden ◽  
Simone Tanelli ◽  
Ousmane Sy ◽  
...  
Keyword(s):  
Weather Forecasting ◽  
Subsequent Development ◽  
Convective Cloud ◽  
Convective Precipitation ◽  
Joint Analysis ◽  
Wind Fields ◽  
Precipitation Radar ◽  
Convective Processes ◽  
Air Motion ◽  
Wind Profiles

Abstract. The mechanisms linking convection and cloud dynamical processes are major factors in much of the uncertainty in both weather and climate prediction. Further constraining the uncertainty in convective cloud processes linking 3-D air motion and cloud structure through models and observations is vital for improvements in weather forecasting and understanding limits on atmospheric predictability. To date, there have been relatively few airborne observations specifically targeted for linking the 3-D air motion surrounding developing clouds to the subsequent development (or nondevelopment) of convective precipitation. During the May–June 2017 Convective Processes Experiment (CPEX), NASA DC-8-based airborne observations were collected from the JPL Ku- and Ka-band Airborne Precipitation Radar (APR-2) and the 2 µm Doppler Aerosol Wind (DAWN) lidar during approximately 100 h of flight. For CPEX, the APR-2 provided the vertical air motion and structure of the cloud systems in nearby precipitating regions where DAWN is unable to sense. Conversely, DAWN sampled vertical wind profiles in aerosol-rich regions surrounding the convection but is unable to sense the wind field structure within most clouds. In this paper, the complementary nature of these data are presented from the 10–11 June flight dates, including the APR-2 precipitation structure and Doppler wind fields as well as adjacent wind profiles from the DAWN data.

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