The Nocturnal Wind Speed and Sensible Heat Flux Over Flat Terrain

2020 ◽  
Vol 176 (3) ◽  
pp. 401-413
Author(s):  
A. Lapworth ◽  
S. R. Osborne
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Flat Terrain

scholarly journals Analysis of Local Air–Sea Interaction in East Asia Using a Regional Air–Sea Coupled Model

2012 ◽  
Vol 25 (2) ◽  
pp. 767-776 ◽  
Author(s):  
Huang Qian ◽  
Yao Suxiang ◽  
Zhang Yaocun
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Solar Radiation ◽  
South China Sea ◽  
Climate Model ◽  
Sensible Heat Flux ◽  
Coupled Model ◽  
Sea Surface ◽  
Sensible Heat ◽  
Flux Evaporation

Abstract A regional air–sea coupled climate model based on the third regional climate model (RegCM3) and the regional oceanic model [the Princeton Ocean Model (POM)] is used to analyze the local air–sea interaction over East Asia in this study. The results indicate that the simulated sea surface temperature (SST) of the coupled model RegCM3–POM is reasonably accurate, and that the spatial pattern and temporal variation are consistent with that of the Global Sea Ice and Sea Surface Temperature dataset (GISST). The correlation between the SST and the atmospheric variables shows that the uncoupled model RegCM3 forced by the given SST cannot reproduce the real-time and SST lag correlation between SST and precipitation, and between SST and surface wind speed, whereas the relationship in the coupled model RegCM3–POM is reasonably accurate. RegCM3–POM reflects the air–sea interaction in the South China Sea and western Pacific Ocean, where the SST lead correlation is the inverse of the SST lag correlation between SST and precipitation, and strong winds bring warm water to the midlatitudes, so the correlation between wind speed and SST is negative in low latitudes and positive in the Kuroshio area. The uncoupled model fails to reproduce the effect of the atmosphere on the ocean. The further study on air–sea interaction in the South China Sea indicates that the earlier warm seawater corresponds to strong sensible heat flux, evaporation, precipitation, and weak net solar radiation, and the early strong sensible heat flux, evaporation, wind at the 10-m level, and weak net solar radiation cause the cold SST.

Sensible Heat Flux in Near-Neutral Conditions over the Sea

2012 ◽  
Vol 42 (7) ◽  
pp. 1134-1142 ◽  
Author(s):  
L. Mahrt ◽  
Dean Vickers ◽  
Edgar L Andreas ◽  
Djamal Khelif
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Surface Temperature ◽  
Sensible Heat Flux ◽  
Sea Surface ◽  
Sensible Heat ◽  
Stable Conditions ◽  
Weakly Stable ◽  
Weak Winds ◽  
Neutral Conditions

Abstract The variation of the sea surface sensible heat flux is investigated using data from the Gulf of Tehuantepec Experiment (GOTEX) and from eight additional aircraft datasets representing a variety of surface conditions. This analysis focuses on near-neutral conditions because these conditions are common over the sea and are normally neglected, partly because of uncertain reliability of measurements of the small air–sea temperature difference. For all of the datasets, upward heat flux is observed for slightly stable conditions. The frequency of this “countergradient” heat flux increases with increasing wind speed and is possibly related to sea spray or microscale variations of surface temperature on the wave scale. Upward area-averaged sensible heat flux for slightly stable conditions can also be generated by mesoscale heterogeneity of the sea surface temperature (SST). Significant measurement errors cannot be ruled out. The countergradient heat flux for weakly stable conditions is least systematic for weaker winds, even though it occurs with weak winds in all of the datasets. In an effort to reduce offset errors and different SST processing and calibration procedures among field programs, the authors adjusted the SST in each field program to minimize the countergradient flux for weak winds. With or without this adjustment for the combined dataset, the extent of the upward heat flux for weakly stable conditions increases with increasing wind speed.

scholarly journals Estimation of Sensible Heat Flux and Atmospheric Boundary Layer Height Using an Unmanned Aerial Vehicle

Atmosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 363 ◽  
Author(s):  
Min-Seong Kim ◽  
Byung Hyuk Kwon
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Unmanned Aerial Vehicle ◽  
Sensible Heat Flux ◽  
Eddy Correlation ◽  
Sensible Heat ◽  
Aerial Vehicle ◽  
Transfer Method

In this work, sensible heat flux estimated using a bulk transfer method was validated with a three-dimensional ultrasonic anemometer or surface layer scintillometer at various sites. Results indicate that it remains challenging to obtain temperature and wind speed at an appropriate reference height. To overcome this, alternative observations using an unmanned aerial vehicle (UAV) were considered. UAV-based wind speed and sensible heat flux were indirectly estimated and atmospheric boundary layer (ABL) height was then derived using the sensible heat flux data. UAV-observed air temperature was measured by attaching a temperature sensor 40 cm above the rotary-wing of the UAV, and UAV-based wind speed was estimated using attitude data (pitch, roll, and yaw angles) recorded using the UAV’s inertial measurement unit. UAV-based wind speed was close to the automatic weather system-observed wind speed, within an error range of approximately 10%. UAV-based sensible heat flux estimated from the bulk transfer method corresponded with sensible heat flux determined using the eddy correlation method, within an error of approximately 20%. A linear relationship was observed between the normalized UAV-based sensible heat flux and radiosonde-based normalized ABL height.

scholarly journals Calculation of sensible-heat flux over a melting ice surface using simple climate data and daily measurements of ablation

2009 ◽  
Vol 50 (50) ◽  
pp. 9-15 ◽  
Author(s):  
Roger J. Braithwaite
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Wind Speed ◽  
Transfer Coefficient ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Climate Data ◽  
Transfer Coefficients ◽  
Monthly Basis

AbstractSensible-heat flux is obviously important for glacier ablation but is difficult to measure routinely. Sensible-heat flux can be estimated from wind-speed and temperature data using a dimensionless heat-transfer coefficient. Values of the heat-transfer coefficient are evaluated for six sites by correlating measured melt energy with a wind–temperature variable (product of daily mean wind speed, temperature and mean atmospheric pressure for the altitude in question). Data are available for short periods from two sites in Arctic Canada and two sites in North Greenland, and for hundreds of days of record at Nordbogletscher and Qamanârssûp sermia in South and West Greenland, respectively. Average transfer coefficients for four out of the six sites are close to 0.003, which is in reasonable agreement with values reported elsewhere, while larger values of 0.0047 and 0.0057 are found at the other two sites. Heat-transfer coefficients are also estimated on a monthly basis for the two long records, and substantial variations are found, suggesting that the method should not be used for <20–30 days of data. The present study is based on manually observed ablation and climate data, but the approach could be updated to use data from automatic recording stations using modern sensors.

scholarly journals A database of water and heat observations over grassland in the north-east of Japan

2018 ◽  
Vol 10 (4) ◽  
pp. 2295-2309 ◽  
Author(s):  
Wenchao Ma ◽  
Jun Asanuma ◽  
Jianqing Xu ◽  
Yuichi Onda
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Wind Speed ◽  
Sensible Heat Flux ◽  
Soil Heat Flux ◽  
Shortwave Radiation ◽  
Sensible Heat ◽  
Net Radiation ◽  
North East ◽  
The North

Abstract. A highly valuable database of long-term hydrometeorological measurements is presented, containing in situ observations for a period of 37 years from a well-maintained grassland in the north-east of Japan. The observations include shortwave radiation, net radiation, air and dew point temperatures at three elevations, soil temperature at four depths, sensible heat flux, soil heat flux, wind speed, relative humidity, air pressure and precipitation. The heights of measurements are 1.6, 12.5 and 29.5 m above ground, with the soil-layer observations at depths of 0.02, 0.1, 0.5 and 1 m. This high-quality database includes four temporal resolutions of 10 s, 0.5 h, 1 h and 24 h, with the hourly data presented here. Monthly and annual statistics are presented at the database web page of the Center for Research in Isotopes and Environmental Dynamics and Prediction of the University of Tsukuba, http://doi.org/10.24575/0001.198108. We validated the data by comparing them with published data from the local meteorological agency in Tateno operated by the Japan Metrological Agency, including the average, maximum and minimum values of air temperature, shortwave radiation, wind speed, relative humidity and precipitation. We have generated a daily downward longwave radiation time series with a method developed by Kondo and Xu (1997) based on the observations from the database. This constructed time series agrees well with observations collected between 2002 and 2006, as evaluated based on the values of the Nash–Sutcliffe efficiency (=0.947) and percent bias (=1.486). For the whole database, annually averaged values show a positive trend in precipitation, air temperature, shortwave radiation, net radiation and sensible heat flux over the past 37 years, with a negative trend detected for wind speed, soil heat flux and soil temperature.

scholarly journals A Study of Nocturnal Surface Wind Speed Overprediction by the WRF-ARW Model in Southeastern Texas

2013 ◽  
Vol 52 (12) ◽  
pp. 2638-2653 ◽  
Author(s):  
Fong Ngan ◽  
Hyuncheol Kim ◽  
Pius Lee ◽  
Khalid Al-Wali ◽  
Bright Dornblaser
Keyword(s):  
Heat Flux ◽  
High Pressure ◽  
Wind Speed ◽  
Surface Wind ◽  
Sensible Heat Flux ◽  
Sea Breeze ◽  
Surface Wind Speed ◽  
Sensible Heat ◽  
Pressure System ◽  
Arw Model

AbstractThe overprediction of surface wind speed during nighttime by the Advanced Research core of the Weather Research and Forecasting (WRF-ARW) model was investigated for a period of the Second Texas Air Quality Study (28 May–3 July 2006). In coastal regions of southeastern Texas, the model had a significant increase of wind speed biases on the surface in the evening throughout the period, especially between 4 and 12 June. The synoptic pattern was a high pressure system centered over the Louisiana–Mississippi area that was subjected to a weak easterly–southeasterly flow in the lower troposphere. The weather conditions favorable for sea-breeze development brought a southerly–southwesterly onshore flow to the near-surface levels. In comparison with measurements, the downward sensible heat flux was overpredicted at night, which resulted in a warm bias in surface temperature. For the vertical wind profile on days with an evening wind bias, sea-breeze-driven nocturnal low-level jets (southerly–southwesterly) were present at around 300 m while another wind maximum was observed at higher levels (around 1.5–2 km), which were associated with a high pressure system centered on southeastern states. The vertical gradient of wind speed in the lowest 150 m was smoother in the model than it was in the observations; this could be attributed to excessive downward mixing. Sensitivities using different land surface and PBL parameterizations showed that the model's overprediction of nocturnal wind was still present despite improvements in the predictions of surface temperature and sensible heat flux.

scholarly journals Environmental Conditions Associated with Horizontal Convective Rolls, Cellular Convection, and No Organized Circulations

2021 ◽  
Author(s):  
Sean R. Santellanes ◽  
George S. Young ◽  
David J. Stensrud ◽  
Matthew R. Kumjian ◽  
Ying Pan
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Discriminant Analysis ◽  
Wind Speed ◽  
Environmental Conditions ◽  
Environmental Variables ◽  
Sensible Heat Flux ◽  
Sensible Heat ◽  
Linear Discriminant ◽  
Convective Rolls

AbstractTypical environmental conditions associated with horizontal convective rolls (HCRs) and cellular convection have been known for over 50 years. Yet our ability to predict whether HCRs, cellular convection, or no discernable organized (null) circulation will occur within a well-mixed convective boundary layer based upon easily observed environmental variables has been limited. Herein, a large data base of 50 cases each of HCR, cellular convection, and null events is created that includes observations of mean boundary layer wind and wind shear, boundary layer depth, and surface observations of wind, temperature, relative humidity, and estimates of surface sensible heat flux. Results from a multi-class linear discriminant analysis applied to these data indicate that environmental conditions can be useful in predicting whether HCRs, cellular convection, or no circulation occurs, with the analysis identifying the correct circulation type on 72% of the case days. This result is slightly better than using a mean CBL wind speed of 6 m s-1 to discriminate between HCRs and cells. However, the mean CBL wind speed has no ability to further separate out cases with no CBL circulation. The key environmental variables suggested by the discriminant analysis are mean sensible heat flux, friction velocity, and the Obukhov length.

scholarly journals A database of water and heat observations over grassland in the north-east of Japan

2018 ◽  
Author(s):  
Wenchao Ma ◽  
Jun Asanuma ◽  
Jianqing Xu ◽  
Yuichi Onda
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Wind Speed ◽  
Sensible Heat Flux ◽  
Soil Heat Flux ◽  
Shortwave Radiation ◽  
Sensible Heat ◽  
Net Radiation ◽  
North East ◽  
The North

Abstract. A highly valuable database of long-term hydro–meteorological measurements is presented, containing in situ observations for a period of 37 years from well-maintained grassland in the north-east of Japan. The observations include the shortwave radiation, net radiation, the air and dew point temperatures at three elevations, the soil temperature at four depths, the sensible heat flux, soil heat flux, wind speed, relative humidity, air pressure and precipitation. The heights of measurements are 1.6 m, 12.5 m and 29.5 m above ground, with the soil-layer observations at depths of −0.02 m, −0.1 m, −0.5 m and −1 m. This high-quality database includes the four temporal resolutions of 10 s, 0.5 h, 1 h and 24 h, with the hourly data presented here. The monthly and annual statistics are presented at the database web page of the Center for Research in Isotopes and Environmental Dynamics and Prediction of the University of Tsukuba, http://doi.org/10.24575/0001.198108 . We have validated the data quality by comparing with published data from the local meteorological agency in Tateno operated by the Japan Metrological Agency, including the average, maximum and minimum values of air temperature, shortwave radiation, wind speed, relative humidity, and precipitation. We have generated a daily downward longwave radiation time series with a method developed by Konto and Xu (1997) based on the observations from the database. This constructed time series agrees well with observations collected between 2002 to 2006, as evaluated based on the values of the Nash–Sutcliffe efficiency (=0.947) and the percent bias (=1.486). For the whole database, annually averaged values give an obvious positive trend in the precipitation, air temperature, shortwave radiation, net radiation and sensible heat flux over the previous 37 years, with a negative trend detected for the wind speed, soil heat flux and soil temperature.

Sign in / Sign up

Export Citation Format

Share Document