Surface-based precipitation phase determination methods in hydrological models

2012 ◽  
Vol 44 (1) ◽  
pp. 44-57 ◽  
Author(s):  
James Feiccabrino ◽  
David Gustafsson ◽  
Angela Lundberg
Keyword(s):  
Air Temperature ◽  
Dew Point ◽  
Temperature Threshold ◽  
Phase Determination ◽  
Probability Curve ◽  
Linear Decrease ◽  
Meteorological Observations ◽  
Second Category ◽  
Model Precipitation ◽  
Precipitation Phase

We compared solid and liquid precipitation mass output from three categories of common model precipitation phase determination schemes (PPDS) to the recorded precipitation phase in a set of 45 years of 3-hour manual meteorological observations from 19 Swedish meteorological stations. In the first category of rain/snow thresholds, it was found that rain/snow air temperature threshold (ATT) is a better precipitation phase indicator than a rain/snow dew point temperature threshold. When a rain/snow ATT of 0.0 °C (a default value used in some recent models) was replaced by 1.0 °C, misclassified precipitation was reduced by almost one half. A second category of PPDS use two ATTs, one snow and one rain, with a linear decrease in snow fraction between. This category identified precipitation phase better than a rain/snow ATT at 17 stations. Using all observations from all the meteorological stations, a final category using an air-temperature-dependent snow probability curve resulted in slightly lower misclassified precipitation mass at 13 of the 19 stations. However, schemes from the linear decrease in snow fraction category had the lowest misclassified precipitation mass at four meteorological stations.

scholarly journals Precipitation phase uncertainty in cold region conceptual models resulting from meteorological forcing time-step intervals

2020 ◽  
Vol 51 (2) ◽  
pp. 180-187
Author(s):  
James M. Feiccabrino
Keyword(s):  
Air Temperature ◽  
Climate Models ◽  
Phase Error ◽  
Dew Point ◽  
Time Step ◽  
Meteorological Forcing ◽  
Surface Precipitation ◽  
Phase Uncertainty ◽  
Meteorological Observations ◽  
Precipitation Phase

Abstract Precipitation phase determination is a known source of uncertainty in surface-based hydrological, ecological, safety, and climate models. This is primarily due to the surface precipitation phase being a result of cloud and atmospheric properties not measured at surface meteorological or hydrological stations. Adding to the uncertainty, many conceptual hydrological models use a 24-h average air temperature to determine the precipitation phase. However, meteorological changes to atmospheric properties that control the precipitation phase often substantially change at sub-daily timescales. Model uncertainty (precipitation phase error) using air temperature (AT), dew-point temperature (DP), and wet-bulb temperature (WB) thresholds were compared using averaged and time of observation readings at 1-, 3-, 6-, 12-, and 24-h periods. Precipitation phase uncertainty grew 35–65% from the use of 1–24 h data. Within a sub-dataset of observations occurring between AT −6 and 6 °C representing 57% of annual precipitation, misclassified precipitation was 7.9% 1 h and 11.8% 24 h. Of note, there was also little difference between 1 and 3 h uncertainty, typical time steps for surface meteorological observations.

scholarly journals Improving surface-based precipitation phase determination through air mass boundary identification

2012 ◽  
Vol 43 (3) ◽  
pp. 179-191 ◽  
Author(s):  
James Feiccabrino ◽  
Angela Lundberg ◽  
David Gustafsson
Keyword(s):  
Air Temperature ◽  
Surface Air Temperature ◽  
Lower Atmosphere ◽  
Temperature Threshold ◽  
Hydrological Models ◽  
Atmospheric Conditions ◽  
Threshold Method ◽  
Phase Determination ◽  
Air Mass ◽  
Precipitation Phase

Most hydrological models apply one empirical formula based on surface air temperature for precipitation phase determination. This approach is flawed as surface precipitation phase results from energy exchanges between falling precipitation and air in the lower atmosphere. Different lower atmospheric conditions cause different precipitation phase probabilities for near-freezing temperatures. Often directly measured lower atmospheric conditions are not available for remote areas. However, meteorological observations occurring before/after similar air mass boundaries have similar atmospheric conditions that vary from most other observations. Therefore, hydrological models can indirectly account for lower atmospheric conditions. Twenty years of manual observations from eight United States weather stations were used to compare misclassified precipitation proportions when analyzing (a) all precipitation observations together and (b) identified cold air mass boundary observations (CAB) and non-CAB observations separately. The CAB observations were identified by a rapid surface air temperature decrease. A two-surface air temperature threshold method with one threshold all snow (TS°C) and one all rain (TR°C) having a linear snow fraction decrease between the thresholds was used. The TS (0 °C), and TR (4 °C) values for CAB were 1 °C warmer than for non-CAB (−1 °C, 3 °C). Analyzing CAB and non-CAB separately reduced misclassified precipitation 23%, from 7.0 to 5.4%.

scholarly journals Reducing misclassified precipitation phase in conceptual models using cloud base heights and relative humidity to adjust air temperature thresholds

2021 ◽  
Author(s):  
Lic James M. Feiccabrino
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Conceptual Models ◽  
Phase Changes ◽  
Cloud Base ◽  
Temperature Threshold ◽  
Air Temperatures ◽  
Low Cloud ◽  
Precipitation Phase ◽  
Cloud Base Height

Abstract In cold region, conceptual models assigned precipitation phase, liquid (rain) or solid (snow), cause vastly different atmospheric, hydrological, and ecological responses, along with significant differences in evaporation, runoff, and infiltration fates for measured precipitation mass. A set air temperature threshold (ATT) applied to the over 30% annual precipitation events occurring with surface air temperatures between −3 and 5 °C resulted in 11.0 and 9.8% misclassified precipitation in Norway and Sweden, respectively. Surface air temperatures do not account for atmospheric properties causing precipitation phase changes as snow falls toward the ground. However, cloud base height and relative humidity (RH) measured from the surface can adjust ATT for expected hydrometeor-atmosphere interactions. Applying calibrated cloud base height ATTs or a linear RH function for Norway (Sweden) reduced to 4.3% (2.8%) and 14.6% (8.9%) misclassified precipitation, respectively. Cloud base height ATTs had lower miss-rates with low cloud bases, 100 m in Norway and 300 m in Sweden. Combining the RH method with cloud base ATT in low cloud conditions resulted in 16.1 and 10.8% reduction in misclassified precipitation in Norway and Sweden, respectively. Therefore, the conceptual model output should improve through the addition of available surface data without coupling to an atmospheric model.

scholarly journals Solar Radiation, Air Temperature, Relative Humidity, and Dew Point Study: Damak, Jhapa, Nepal

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Arun Kumar Shrestha ◽  
Arati Thapa ◽  
Hima Gautam
Keyword(s):  
Relative Humidity ◽  
Solar Radiation ◽  
Air Temperature ◽  
Gaussian Function ◽  
Great Influence ◽  
Dew Point ◽  
Upward Trend ◽  
Summer Maximum ◽  
Online Calculator ◽  
Climatic Phenomenon

Monitoring and prediction of the climatic phenomenon are of keen interest in recent years because it has great influence in the lives of people and their environments. This paper is aimed at reporting the variation of daily and monthly solar radiation, air temperature, relative humidity (RH), and dew point over the year of 2013 based on the data obtained from the weather station situated in Damak, Nepal. The result shows that on a clear day, the variation of solar radiation and RH follows the Gaussian function in which the first one has an upward trend and the second one has a downward trend. However, the change in air temperature satisfies the sine function. The dew point temperature shows somewhat complex behavior. Monthly variation of solar radiation, air temperature, and dew point shows a similar pattern, lower at winter and higher in summer. Maximum solar radiation (331 Wm-2) was observed in May and minimum (170 Wm-2) in December. Air temperature and dew point had the highest value from June to September nearly at 29°C and 25°C, respectively. The lowest value of the relative humidity (55.4%) in April indicates the driest month of the year. Dew point was also calculated from the actual readings of air temperature and relative humidity using the online calculator, and the calculated value showed the exact linear relationship with the observed value. The diurnal and nocturnal temperature of each month showed that temperature difference was relatively lower (less than 10°C) at summer rather than in winter.

Measurement of indoor environmental parameters and analysis of the condensation phenomenon in urban utility tunnels

2022 ◽  
pp. 1420326X2110564
Author(s):  
Chuanmin Tai ◽  
Guansan Tian ◽  
Wenjun Lei
Keyword(s):  
Water Supply ◽  
Surface Temperature ◽  
Air Temperature ◽  
Natural Ventilation ◽  
Environmental Parameters ◽  
Dew Point ◽  
Control Mode ◽  
Safe Management ◽  
Environmental Test ◽  
Water Supply Pipeline

Condensation is a major issue in the safe operation of utility tunnels. To address the condensation problem, the indoor air temperature, relative humidity (RH) and surface temperature in an urban utility tunnel in Jining were continuously measured, and the condensation conditions were surveyed and analysed. The results indicated that under natural ventilation conditions, the air temperature in the comprehensive cabin varied from 23.4°C to 24.5°C, the RH fluctuated between 86.4% and 95.3%, and the corresponding air dew point temperature (DPT) remained in the range of 22.2°C–22.9°C. The surface temperature of the water supply pipeline ranged from 17.8°C to 18.5°C, which was far lower than the DPT in the tunnel, resulting in serious condensation. A water supply pipeline with an anti-condensation design was developed based on environmental test data. A 25-mm-thick rubber plastic sponge insulation layer was used to thermally insulate the water supply pipeline, preventing further dew condensation. Furthermore, mechanical ventilation had little effect on reducing the RH in the tunnel and may actually cause dew condensation; therefore, a ventilation control mode was proposed in this study. These results are expected to provide basic data for further research and reference for the safe management of utility tunnels.

Modelling pavement temperature for winter maintenance operations

2004 ◽  
Vol 31 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Aly Sherif ◽  
Yasser Hassan
Keyword(s):  
Surface Temperature ◽  
Air Temperature ◽  
Negative Impact ◽  
Weather Conditions ◽  
Statistical Modelling ◽  
Dew Point ◽  
Road Maintenance ◽  
Winter Maintenance ◽  
Pavement Surface ◽  
Pavement Temperature

Road and highway maintenance is vital for the safety of citizens and for enabling emergency and security services to perform their essential functions. Accumulation of snow and (or) ice on the pavement surface during the wintertime substantially increases the risk of road crashes and can have negative impact on the economy of the region. Recently, road maintenance engineers have used pavement surface temperature as a guide to the application of deicers. Stations for road weather information systems (RWIS) have been installed across Europe and North America to collect data that can be used to predict weather conditions such as air temperature. Modelling pavement surface temperature as a function of such weather conditions (air temperature, dew point, relative humidity, and wind speed) can provide an additional component that is essential for winter maintenance operations. This paper uses data collected by RWIS stations at the City of Ottawa to device a procedure that maximizes the use of a data batch containing complete, partially complete, and unusable data and to study the relationship between the pavement surface temperature and weather variables. Statistical models were developed, where stepwise regression was first applied to eliminate those variables whose estimated coefficients are not statistically significant. The remaining variables were further examined according to their contribution to the criterion of best fit and their physical relationships to each other to eliminate multicollinearities. The models were further corrected for the autocorrelation in their error structures. The final version of the developed models may then be used as a part of the decision-making process for winter maintenance operations.Key words: winter maintenance, pavement temperature, statistical modelling, RWIS.

scholarly journals A temperature threshold to identify the driving climate forces of the respiratory process in terrestrial ecosystems

2017 ◽  
Author(s):  
Zhiyuan Zhang ◽  
Renduo Zhang ◽  
Yang Zhou ◽  
Alessandro Cescatti ◽  
Georg Wohlfahrt ◽  
...  
Keyword(s):  
Air Temperature ◽  
Driving Forces ◽  
Ecosystem Respiration ◽  
Large Fraction ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
Co2 Concentration ◽  
Temperature Threshold ◽  
Current Scenario ◽  
Ecosystem Flux

Abstract. Terrestrial ecosystem respiration (Re) is the major source of CO2 release and constitutes the second largest carbon flux between the biosphere and atmosphere. Therefore, climate-driven changes of Re may greatly impact on future atmospheric CO2 concentration. The aim of this study was to derive an air temperature threshold for identifying the driving climate forces of the respiratory process in terrestrial ecosystems within different temperature zones. For this purpose, a global dataset of 647 site-years of ecosystem flux data collected at 152 sites has been examined. Our analysis revealed an ecosystem threshold of mean annual air temperature (MAT) of 11 ± 2.3 °C. In ecosystems with the MAT below this threshold, the maximum Re rates were primarily dependent on temperature and respiration was mainly a temperature-driven process. On the contrary, in ecosystems with the MAT greater than 11 ± 2.3 °C, in addition to temperature, other driving forces, such as water availability and surface heat flux, became significant drivers of the maximum Re rates and respiration was a multi-factor-driven process. The information derived from this study highlight the key role of temperature as main controlling factor of the maximum Re rates on a large fraction of the terrestrial biosphere, while other driving forces reduce the maximum Re rates and temperature sensitivity of the respiratory process. These findings are particularly relevant under the current scenario of rapid global warming, given that the potential climate-induced changes in ecosystem respiration may lead to substantial anomalies in the seasonality and magnitude of the terrestrial carbon budget.

scholarly journals Estudo de Frequência da Ocorrência de Rajada de Vento e seu Papel na Segurança das Operações Aéreas no Aeródromo Internacional de Belém-PA (Wind Occurrence Frequency Study and Its Importance in Air Operations Security on Belém's International Aerodrome)

2015 ◽  
Vol 7 (6) ◽  
pp. 1110
Author(s):  
Ingrid Monteiro Peixoto de Souza ◽  
Thiago Melo Souza ◽  
José Danilo Costa Souza Filho ◽  
Maria do Carmo Felipe de Oliveira ◽  
Dimitrie Nechet
Keyword(s):  
Air Temperature ◽  
Atmospheric Pressure ◽  
Occurrence Frequency ◽  
Equatorial Atlantic ◽  
Flight Operations ◽  
Equatorial Atlantic Ocean ◽  
Meteorological Observations ◽  
Maximum Temperatures ◽  
Meteorological Elements ◽  
Wind Intensity

Este trabalho teve como objetivo estudar a freqüência de ocorrência de rajada de vento e sua importância na segurança das operações aéreas, uma vez que estas apresentam significativas variações de intensidade do vento, podendo ocasionar, inúmeros riscos para a aviação, desde desconforto durante o voo, até perdas de vidas humanas. Os dados foram obtidos no Aeródromo Internacional de Belém do Pará, no período de 2009 a 2012, onde foram realizadas análises estatísticas, bem como, estudos das correlações dos percentuais de ocorrências com os elementos meteorológicas de superfície (temperatura do ar e pressão atmosférica), extraídas de observações meteorológicas horárias da localidade em estudo. Os resultados mostram, que nos últimos anos, a ocorrência de rajada de vento no aeródromo de Belém-Pa, vem aumentando, onde o maior registro dessa ocorrência dentro do período foi no ano de 2012. A maior frequência de eventos de rajada por intervalos de velocidade foi de 21 a 30 KT. A maior distribuição sazonal do registro de rajadas de vento ocorreu no período mais chuvoso da região, dezembro a maio, influenciadas pela nebulosidade, formada no Oceano Atlântico Equatorial, devido a atuação da ZCIT. As maiores quantidades de registros de rajadas de ventos correspondem ao período de máximas temperaturas, sugerindo uma correlação entre o aquecimento e a ocorrência de rajadas próximas a superfície terrestre. A distribuição de rajada de vento, de acordo com a orientação do vento indica predominância dos ventos de leste, de 60º a 120º.  ABSTRACT This paper aimed to study the wind occurrence frequency and its importance on the safety of flight operations, since these are significant variations in wind intensity, causing many risks to aviation, from discomfort during flight to even loss of lifes. The data were obtained from the International Aerodrome of Belém do Pará, in the period from 2009 to 2012, where statistical analyzes were performed, as well as studies of correlations of the percentage of occurrences with surface meteorological elements (air temperature and atmospheric pressure), extracted from hourly meteorological observations from the study site. The results show that in recent years, the occurrence of gust of wind at the airfield of Belém-Pa, is increasing, where the highest record of this occurrence within the period was in 2012. The higher frequency of events per burst speed intervals was 21-30 KT. The largest seasonal distribution record wind gusts occurred in the rainy season in the region, from December to May, influenced by clouds formed in the Equatorial Atlantic Ocean, due to tripping of the ITCZ​. The largest amounts of records gusty winds correspond to the period of maximum temperatures, suggesting a correlation between warming and the occurrence of near Earth's surface bursts. The distribution of wind, according to the orientation of the wind indicates predominance of winds east 60 º to 120 º.   Keywords: Wind direction, air temperature, atmospheric pressure.  

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