scholarly journals A physically based method for correcting temperature data measured by naturally ventilated sensors over snow

2001 ◽  
Vol 47 (159) ◽  
pp. 665-670 ◽  
Author(s):  
Martin Arck ◽  
Dieter Scherer
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Measurement Errors ◽  
Correction Method ◽  
Temperature Data ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Low Wind Speed ◽  
Snowmelt Period ◽  
Physically Based

AbstractDuring the snowmelt period in 1998, air-temperature data were acquired at 1 min intervals using different measurement systems as part of a field campaign in the Kärkevagge, Swedish Lapland. A comparison reveals that temperatures from naturally ventilated sensors exceed temperatures from aspirated sensors by as much as 6.2 K. Errors in temperature are closely connected to high values of upwelling shortwave radiation and are larger in periods of low wind speed. Measurement errors result from the instantaneous radiation conditions and propagate over the next measurements due to slow response time of the naturally ventilated sensor. A physically based method is developed for correcting temperature data influenced by radiation errors, which requires additional measurements of wind speed and upwelling shortwave radiation. Coefficients of the correction formula are automatically determined from the erroneous temperature data, so the method is independent of accurate air-temperature measurements. The high quality of the correction method could be validated by accurate psychrometer measurements. One of the most important applications is the computation of sensible-heat fluxes from snow-covered surfaces during the snowmelt period using the bulk-aerodynamic method, which is greatly improved by the new correction method.

scholarly journals Correlation and Causation Analysis Between COVID-19 and Environmental Factors in China

2021 ◽  
Vol 3 ◽  
Author(s):  
Zuofang Zheng ◽  
Junxia Dou ◽  
Conglan Cheng ◽  
Hua Gao
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Regional Climate ◽  
Climate Impact ◽  
Control Measures ◽  
Specific Humidity ◽  
Human Society ◽  
Causality Test ◽  
Low Wind Speed ◽  
Causation Analysis

Coronavirus disease 2019 (COVID-19) is seriously threatening and altering human society. Although prevention and control measures play an important role in preventing the transmission of severe acute respiratory syndrome coronavirus, signals of climate impact can still be detected globally. In this paper, the data of 265 cities in China were analyzed. The results show that the correlations between COVID-19 and air quality index (AQI) and PM2.5 concentration were very weak and that the correlations between COVID-19 and meteorological factors were significantly different in different climate backgrounds. So, a fixed model is not enough to describe the correlations. Overall, high humidity, low wind speed, and relatively lower air temperature are conducive to the spread of COVID-19. The climate background suitable for the spread of COVID-19 in China is air temperature 0~15°C, specific humidity <3 g kg−1, and wind speed <3 m s−1. The Granger causality test shows that there is a causal relationship between daily average air temperature and the number of COVID-19 confirmed cases in some cities of China, and air temperature is indicative of the number of confirmed cases the next day. However, this phenomenon is not universal due to regional climate differences.

scholarly journals Effects of clouds on surface melting of Laohugou glacier No. 12, western Qilian Mountains, China

2018 ◽  
Vol 64 (243) ◽  
pp. 89-99 ◽  
Author(s):  
JIZU CHEN ◽  
XIANG QIN ◽  
SHICHANG KANG ◽  
WENTAO DU ◽  
WEIJUN SUN ◽  
...  
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Meteorological Data ◽  
Water Vapor Pressure ◽  
Longwave Radiation ◽  
Turbulent Heat Flux ◽  
Qilian Mountains ◽  
Shortwave Radiation ◽  
Turbulent Heat ◽  
Glacier Melt

ABSTRACTWe analyzed a 2-year time series of meteorological data (January 2011–December 2012) from three automatic weather stations on Laohugou glacier No. 12, western Qilian Mountains, China. Air temperature, humidity and incoming radiation were significantly correlated between the three sites, while wind speed and direction were not. In this work, we focus on the effects of clouds on other meteorological parameters and on glacier melt. On an average, ~18% of top-of-atmosphere shortwave radiation was attenuated by the clear-sky atmosphere, and clouds attenuated a further 12%. Most of the time the monthly average increases in net longwave radiation caused by clouds were larger than decreases in net shortwave radiation but there was a tendency to lose energy during the daytime when melting was most intense. Air temperature and wind speed related to turbulent heat flux were found to suppress glacier melt during cloudy periods, while increased water vapor pressure during cloudy days could enhance glacier melt by reducing energy loss by latent heat. From these results, we have increased the physical understanding of the significance of cloud effects on continental glaciers.

scholarly journals Three novel copula-based bias correction methods for daily ECMWF air temperature data

2017 ◽  
Author(s):  
Fakhereh Alidoost ◽  
Alfred Stein ◽  
Zhongbo Su ◽  
Ali Sharifi
Keyword(s):  
Air Temperature ◽  
Bias Correction ◽  
Weather Forecast ◽  
Correction Method ◽  
Temperature Data ◽  
Weather Data ◽  
Conditional Quantiles ◽  
New Methods ◽  
Conditional Copula ◽  
Weather Stations

Abstract. Data retrieved from global weather forecast systems are typically biased with respect to measurements at local weather stations. This paper presents three copula-based methods for bias correction of daily air temperature data derived from the European Centre for Medium-range Weather Forecasts (ECMWF). The aim is to predict conditional copula quantiles at different unvisited locations, assuming spatial stationarity of the underlying random field. The three new methods are: bivariate copula quantile mapping (types I and II), and a quantile search. These are compared with commonly applied methods, using data from an agricultural area in the Qazvin Plain in Iran containing five weather stations. Cross-validation is carried out to assess the performance. The study shows that the new methods are able to predict the conditional quantiles at unvisited locations, improve the higher order moments of marginal distributions, and take the spatial variabilities of the bias-corrected variable into account. It further illustrates how a choice of the bias correction method affects the bias-corrected variable and highlights both theoretical and practical issues of the methods. We conclude that the three new methods improve local refinement of weather data, in particular if a low number of observations is available.

Surface Meteorology and Air–Sea Fluxes in the Southwestern Tropical Atlantic Ocean

2020 ◽  
Author(s):  
Marcelo Dourado ◽  
Carlos Lentini
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Atlantic Ocean ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Surface Fluxes ◽  
Shortwave Radiation ◽  
Tropical Atlantic ◽  
Precipitation Regime ◽  
Average Wind Speed

<p> Recent studies suggest that the Tropical Atlantic Warm Pool (PQAT) contributes to modulate the variability of the ZCIT in the Atlantic Ocean basin and, consequently, the precipitation regime in Brazilian northeastern. Hourly surface meteorology observations from the PIRATA buoy at 19°S, 34°W from August 2010 to November 2018 was used to characterize and estimate the exchanges of heat, freshwater, and momentum between the ocean and the atmosphere over the Tropical. We focus here on recent efforts to observe the surface meteorology and air-sea fluxes using those data to gain insights into how atmospheric variability may govern the structure and variability of the upper ocean there at diurnal and seasonal time scales. The surface fluxes are calculated using the COARE 3.0 algorithm, positive values are to the ocean. Using the observations collected from the mooring deployments, we developed a good understanding of the annual march of the surface forcing of the ocean by the atmosphere. During spring (March, April) mean SST and air temperature are the hottest of the year, 28<sup>o</sup>C and 26.7<sup>o</sup>C, respectively; SST is greater than air temperature all over the year, 1<sup>o</sup>C on average. Wind speed is minimum, the air is drier and there is a peak of precipitation in April. During the autumn (August, September), mean SST and air temperature are the coldest of the year, 24.5<sup>o</sup>C and 23.6<sup>o</sup>C. Wind speed increases form 4.4m/s in March to 5.9 m/s in December. The monthly averaged incoming shortwave radiation in July was the lowest of the whole year and maximum in December. Net longwave radiation shows an inverse variability, i.e., maximum in the winter, minimum in the summer. This occurs because the winter air is drier than in the summer. Sensible heat flux is maximum in August due to the increase of the wind speed and an increase of the air-sea temperature difference. Latent flux is higher between April and August due to an increase in wind speed and a drier atmosphere. In the summer the humidity increases and, consequently, the latent heat flux diminishes. Finally, the net heat flux, positive between January and March, is negative between April and August (maximum -36W/m<sup>2</sup> in July ) and, again, positive between September and December, maximum +116 W/m<sup>2</sup> in December.</p>

Air Temperature Measurement Errors in Naturally Ventilated Radiation Shields

2005 ◽  
Vol 22 (7) ◽  
pp. 1046-1058 ◽  
Author(s):  
Reina Nakamura ◽  
L. Mahrt
Keyword(s):  
Air Temperature ◽  
Measurement Errors ◽  
Radiative Forcing ◽  
Systematic Errors ◽  
Shortwave Radiation ◽  
Platinum Resistance ◽  
Temperature Detector ◽  
Measurement Height ◽  
Definition Of ◽  
Plane Displacement

Abstract Two sources of systematic errors are considered for estimating air temperature. The first source is ambiguity of the definition of the standardized measurement height over vegetated surfaces of varying heights. Without such a standardization, evaluation of the horizontal air temperature gradient is contaminated by the vertical variation of air temperature. This error is generally small in daytime unstable conditions, but increases with increasing stability at night. In an attempt to reduce such error, the use of the zero-plane displacement height for standardizing the measurement height is proposed. The second source of systematic errors is radiative forcing on the sensor–shield systems. A series of experiments is performed over a grass field to investigate the radiatively induced error in the air temperature estimate by the Onset HOBO Pro thermistor in a naturally ventilated multiplate shield. The magnitude of this error is estimated by comparing air temperature measurements by a platinum resistance temperature detector (RTD) sensor in a mechanically aspirated shield. In contrast to the errors resulting from the first source, the radiatively induced error increases with increasing instability. An empirical model is developed for correcting the radiatively induced temperature error using information on wind speed and net or shortwave radiation. The robustness of the model is examined with independent data.

scholarly journals Analysis of the Radiation Fluxes over Complex Surfaces on the Tibetan Plateau

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3084
Author(s):  
Chunxiao Wang ◽  
Yaoming Ma ◽  
Binbin Wang ◽  
Weiqiang Ma ◽  
Xuelong Chen ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Surface Temperature ◽  
Air Temperature ◽  
Surface Albedo ◽  
Longwave Radiation ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
The Tibetan Plateau ◽  
Downward Shortwave Radiation ◽  
Downward Longwave Radiation

Analysis of long-term, ground-based observation data on the Tibetan Plateau help to enhance our understanding of land-atmosphere interactions and their influence on weather and climate in this region. In this paper, the daily, monthly, and annual averages of radiative fluxes, surface albedo, surface temperature, and air temperature were calculated for the period of 2006 to 2019 at six research stations on the Tibetan Plateau. The surface energy balance characteristics of these six stations, which include alpine meadow, alpine desert, and alpine steppe, were then compared. The downward shortwave radiation at stations BJ, QOMS, and NAMORS was found to decrease during the study period, due to increasing cloudiness. Meanwhile, the upward shortwave radiation and surface albedo at all stations were found to have decreased overall. Downward longwave radiation, upward longwave radiation, net radiation, surface temperature, and air temperature showed increasing trends on inter-annual time scales at most stations. Downward shortwave radiation was maximum in spring at BJ, QOMS, NADORS, and NAMORS, due to the influence of the summer monsoon. Upward shortwave radiation peaked in October and November due to the greater snow cover. BJ, QOMS, NADORS, and NAMORS showed strong sensible heat fluxes in the spring while MAWORS showed strong sensible heat fluxes in the summer. The monthly and diurnal variations of surface albedo at each station were “U” shaped. The diurnal variability of downward longwave radiation at each station was small, ranging from 220 to 295 W·m−2.The diurnal variation in surface temperature at each station slightly lagged behind changes in downward shortwave radiation, and the air temperature, in turn, slightly lagged behind the surface temperature.

scholarly journals Construção de cenários futuros da temperatura máxima do ar: Capitais do Nordeste Brasileiro

2021 ◽  
pp. 2427-2445
Author(s):  
Ana Carla dos Santos Gomes ◽  
Maytê Duarte Leal Coutinho ◽  
Fábio de Paula Viana ◽  
Losany Branches Viana ◽  
Sivaldo Filho Seixas Tavares ◽  
...  
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Wind Speed ◽  
Air Temperature ◽  
Temperature Data ◽  
Northeastern Brazil ◽  
Future Scenarios ◽  
General Terms ◽  
Dynamic Regression Model ◽  
Maximum Air Temperature

This research aims to analyze and estimate future scenarios of maximum air temperature in the capitals of northeastern Brazil, in order to highlight the importance of climate change today and in the future. For this, rainfall, wind speed, relative humidity and maximum air temperature data were used by the database meteorological activities of the National Institute of Meteorology, of the nine capitals of the northeastern region of Brazil from 1980 to 2019, and the dynamic regression technique that combines the dynamics of time series and the effect of explanatory variables.The main results showed that the dynamic regression model satisfactorily adjusted the association between meteorological variables.Trend (without lag) and seasonality (lag) functions were considered in all capitals, presenting the occurrence of different lags according to the capital and the variable. Thus, the highest temperatures among the capitals analyzed occurred in Teresina/PI and the least high, in Salvador/BA. In general terms, the optimistic scenarios (C1) presented temperature between 32.5 and 35 ºC, the pessimists (C2) between 37.5 ºC and extremes (C3) 35 and 39 ºC, evidencing that all future scenarios present danger to the population. It is expected that the results obtained can help public policies.

scholarly journals Relative impacts of increases of solar radiation and air temperature on the temperature of surface water in a shallow, eutrophic lake

2021 ◽  
Author(s):  
Ryuichiro Shinohara ◽  
Yoji Tanaka ◽  
Ariyo Kanno ◽  
Kazuo Matsushige
Keyword(s):  
Heat Flux ◽  
Surface Water ◽  
Solar Radiation ◽  
Water Temperature ◽  
Air Temperature ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Surface Water Temperature ◽  
Lake Kasumigaura ◽  
Lake Surface

Abstract We monitored lake surface water temperatures from 1992 to 2019 in Lake Kasumigaura, a shallow lake in Japan. We hypothesized that increases of shortwave radiation had increased surface water temperatures and heat fluxes more than had the increases of air temperature. We used the heat flux analyses and the sensitivity analyses to test the hypothesis. The fluxes of solar radiation gradually increased during the study period in a manner consistent with the phenomenon of global brightening. The increase was especially apparent in the spring. The rate of increase of surface water temperature was especially significant in May. Air temperature did not significantly increase in May, but it increased significantly in June (0.40 °C decade−1). A sensitivity analysis of the heat fluxes at the lake surface (shortwave radiation, longwave radiation, latent heat flux, and sensible heat flux) revealed that surface water temperature was more sensitive to changes of shortwave radiation than to air temperature during the spring. Although other factors such as inflows of groundwater and river water may also have impacted surface water temperatures, the increase of solar radiation appeared to be the major factor responsible for the increase of surface water temperature during the spring in Lake Kasumigaura.

scholarly journals Snow farming: Conserving snow over the summer season

2017 ◽  
Author(s):  
Thomas Grünewald ◽  
Michael Lehning ◽  
Fabian Wolfsperger
Keyword(s):  
Energy Balance ◽  
Laser Scanning ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Wind Speeds ◽  
Physically Based ◽  
Sensitivity Studies ◽  
Wave Emission ◽  
The One ◽  
Snow Mass

Abstract. Summer storage of snow for winter touristic purpose has seen an increasing interest in the last years. Covering large snow piles with materials such as sawdust enables to conserve more than two thirds of the initial snow volume. We present detailed mass balance measurements of two sawdust covered snow piles obtained by terrestrial laser scanning during summer 2015. Results indicate that 74 % and 63 % of the snow volume remained over the summer. If snow mass is considered instead of volume, the values increase to 85 % and 72 % which is attributed to settling and densification of the snow. Additionally, we adapted the one-dimensional, physically based snow cover model SNOWPACK to perform simulations of the sawdust covered snow piles. Model results and measurement agreed extremely well at the point scale. Moreover, we analyzed the contribution of the different terms of the energy balance to snow ablation for a pile covered with a 40 cm thick sawdust layer and a pile without insulation. Shortwave radiation was the dominant source of energy for both scenarios but the moist sawdust caused strong cooling by long-wave emission and negative sensible and latent heat fluxes. This cooling effect reduces the surface energy balance by a factor or 12. As a result only 9 % of the net shortwave energy remained available for melt. Finally, sensitivity studies of the parameters thickness of the sawdust layer, air temperature, precipitation and wind speed were performed. We show that sawdust thickness has a tremendous effect on snow loss. Higher temperatures and wind speeds increase snow ablation but are less important. No significant effect of additional precipitation could be found as the sawdust remained wet during the entire summer. However, switching of precipitation of completely would strongly increase melt.

scholarly journals Surface energy balance of the Sygyktinsky Glacier, south Eastern Siberia, during the ablation period and its sensitivity to meteorological fluctuations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eduard Y. Osipov ◽  
Olga P. Osipova
Keyword(s):  
Energy Balance ◽  
Wind Speed ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Eastern Siberia ◽  
Atmospheric Conditions ◽  
South Eastern ◽  
Glacier Ablation

AbstractThe physically based melt of the low elevation Eastern Siberian glaciers is poorly understood due to the lack of direct micrometeorological studies. We used an automatic meteorological station to record the meteorological and energy characteristics of the Sygyktinsky Glacier, south Eastern Siberia (56.8° N, 117.4° E, 2,560 m a.s.l.), during two ablation seasons and computed the surface energy balance (SEB) for 30-min intervals. The glacier ablation was both modeled and measured by stakes and a thermistor cable. The net radiation (Rnet) was the main contributor (71–75 W m−2, 89–95%) to the SEB (79 W m−2, 100%), followed by sensible (2–4 W m−2, 3–5%) and latent (2–3 W m−2, 2–4%) heat fluxes. The net shortwave radiation was the main positive component of Rnet, while the net longwave radiation was weak and either negative (− 15 W m−2 in 2019) or positive (4 W m−2 in 2020). The small proportion of turbulent fluxes in the SEB is explained by the low wind speed (1.2 m s−1). The glacier ablation was found to be more sensitive to changes in shortwave radiation and wind speed, suggesting the need to consider the atmospheric conditions of the ablation period (summer snowfalls, cloudiness, wind speed) when analyzing long-term trends in glacial changes.

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