scholarly journals Evidence of Very Shallow Summertime Katabatic Flows in Dronning Maud Land, Antarctica

2013 ◽  
Vol 52 (1) ◽  
pp. 164-168 ◽  
Author(s):  
Rostislav Kouznetsov ◽  
Priit Tisler ◽  
Timo Palo ◽  
Timo Vihma
Keyword(s):  
Wind Speed ◽  
Austral Summer ◽  
Multiple Frequency ◽  
Katabatic Flow ◽  
Doppler Sodar ◽  
Wind Speed Maximum ◽  
Measuring Site ◽  
Katabatic Flows ◽  
Dronning Maud Land ◽  
Parallel Mode

AbstractThe three-axis “Latan-3” Doppler sodar was operated near the Finnish Antarctic station Aboa in Dronning Maud Land (73.04°S, 13.40°W) in the austral summer of 2010/11. The measuring site is located at a practically flat, slightly sloped (about 1%) surface of the glacier. The sodar was operated in multiple-frequency parallel mode with 20–800-m sounding range, 20-m vertical resolution, and 10-s temporal resolution. To reveal the wind and temperature profiles below the sounding range as well as turbulent fluxes at 2 and 10 m, the data from a 10-m meteorological mast were used. During the measurements, the atmospheric boundary layer was within the sounding range of the sodar most of the time. Despite a large variety of observed sodar echo patterns and wind speed profiles, several cases of clear steady katabatic flows were observed. Practically all of them were easterly, whereas the uphill direction is southern. The thickness of the katabatic flow varied from a few tens to several hundreds of meters; the wind speed maximum could be as low as 5 m. Thin katabatic flows had lower wind speed and much stronger temperature gradients (up to 1 K m−1) but had smaller surface heat flux than did the thicker ones.

scholarly journals Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

2017 ◽  
Vol 11 (6) ◽  
pp. 2897-2918 ◽  
Author(s):  
Valentina Radić ◽  
Brian Menounos ◽  
Joseph Shea ◽  
Noel Fitzpatrick ◽  
Mekdes A. Tessema ◽  
...  
Keyword(s):  
Wind Speed ◽  
Friction Velocity ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Katabatic Flow ◽  
Glacier Surface ◽  
Mountain Glacier ◽  
Near Surface ◽  
Wind Speed Maximum ◽  
Turbulent Heat Fluxes

Abstract. As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods), commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible- and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddy-covariance (OPEC) method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin–Obukhov (M–O) stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M–O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the KInt method) outperforms any C method in simulating the friction velocity; however, the C methods outperform the KInt method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the KInt approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in the measured meteorological variables and the roughness lengths produce errors in the modeled fluxes that are smaller than the differences between the modeled and observed fluxes. This implies that further advances will require improvement to model theory rather than better measurements of input variables. Further data from different glaciers are needed to investigate any universality of these findings.

scholarly journals Structure of Turbulence in Katabatic Flows Below and Above the Wind-Speed Maximum

2015 ◽  
Vol 159 (3) ◽  
pp. 469-494 ◽  
Author(s):  
Andrey A. Grachev ◽  
Laura S. Leo ◽  
Silvana Di Sabatino ◽  
Harindra J. S. Fernando ◽  
Eric R. Pardyjak ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Speed Maximum ◽  
Katabatic Flows

Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica

2015 ◽  
Vol 54 (7) ◽  
pp. 1393-1412 ◽  
Author(s):  
Dale T. Andersen ◽  
Christopher P. McKay ◽  
Victor Lagun
Keyword(s):  
Wind Speed ◽  
Austral Summer ◽  
Solar Flux ◽  
East Antarctica ◽  
Daily Maximum ◽  
Mean Annual Temperature ◽  
Secondary Source ◽  
Climate Conditions ◽  
Wind Speeds ◽  
Strong Winds

AbstractIn November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 ± 0.6 W m−2. The mean annual temperature at Lake Untersee was determined to be −10.6° ± 0.6°C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were −3.5°, −1.9°, −2.2°, −2.6°, and −2.5°C. The maximum (minimum) temperatures were +5.3°, +7.6°, +5.7°, +4.4°, and +9.0°C (−13.8°, −12.8°, −12.9°, −13.5°, and −12.1°C). The average of the wind speed recorded was 5.4 m s−1, the maximum was 35.7 m s−1, and the average daily maximum was 15 m s−1. The wind speed was higher in the winter, averaging 6.4 m s−1. Summer winds averaged 4.7 m s−1. The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.

scholarly journals Time Series Analysis on Incidence of Pulmonary Tuberculosis With Weather Factors During 2004-2017 in Guangdong Province, China

2021 ◽  
Author(s):  
Tianyu Qin ◽  
Yu Hao ◽  
Juan He
Keyword(s):  
Wind Speed ◽  
Atmospheric Pressure ◽  
Guangdong Province ◽  
Maximum Temperature ◽  
Maximum Pressure ◽  
Weather Factors ◽  
Sarima Model ◽  
Extreme Wind ◽  
Wind Speed Maximum ◽  
Extreme Wind Speed

Abstract Background: Although the occurrence of some infectious diseases including TB was found to be associated with specific weather factors, few studies have incorporated weather factors into the model to predict the incidence of tuberculosis (TB). We aimed to establish an accurate forecasting model using TB data in Guangdong Province, incorporating local weather factors.Methods: Data of sixteen meteorological variables (2003-2016) and the TB incidence data (2004-2016) of Guangdong were collected. Seasonal autoregressive integrated moving average (SARIMA) model was constructed based on the data. SARIMA model with weather factors as explanatory variables (SARIMAX) was performed to fit and predict TB incidence in 2017. Results: Maximum temperature, maximum daily rainfall, minimum relative humidity, mean vapor pressure, extreme wind speed, maximum atmospheric pressure, mean atmospheric pressure and illumination duration were significantly associated with log(TB incidence). After fitting the SARIMAX model, maximum pressure at lag 6 (β= -0.007, P < 0.05, 95% confidence interval (CI): -0.011, -0.002, mean square error (MSE): 0.279) was negatively associated with log(TB incidence), while extreme wind speed at lag 5 (β=0.009, P < 0.05, 95% CI: 0.005, 0.013, MSE: 0.143) was positively associated. SARIMAX (1, 1, 1) (0, 1, 1)12 with extreme wind speed at lag 5 was the best predictive model with lower Akaike information criterion (AIC) and MSE. The predicted monthly TB incidence all fall within the confidence intervals using this model. Conclusions: Weather factors have different effects on TB incidence in Guangdong. Incorporating meteorological factors into the model increased the accuracy of prediction.

scholarly journals Cable Car Speed Control Using Programmable Logic Control Based on Fuzzy Logic

2020 ◽  
Vol 2 (3) ◽  
pp. 125-129
Author(s):  
Santi Triwijaya ◽  
Arief Darmawan ◽  
Andri Pradipta ◽  
Dara Aulia Feriando
Keyword(s):  
Fuzzy Logic ◽  
Wind Speed ◽  
Maximum Load ◽  
Dc Motor ◽  
Programmable Logic ◽  
Logic Control ◽  
Programmable Logic Control ◽  
Wind Speed Maximum ◽  
Safety And Reliability ◽  
Load Weight

A cable car is a hanging car that runs by cable. Cable car carrier controlled by DC motor. The cable car can be a solution to accommodate the mobilization of agricultural commodities in areas that are difficult to access while still paying attention to safety and reliability. In this research, the speed of a cable car would be automatically controlled with Programmable Logic Control (PLC). PLC functions as a cable car operation controller by considering 3 parameters, namely: wind speed, maximum load weight, and distance (meters). The speed of the cable car is controlled by the PLC using fuzzy logic. Cable car speed is based on parameters of wind speed, load weight and distance. From the results obtained, the PLC has worked well in regulating the speed of the cable car and if any parameter exceeds the PLC limit, it can turn off the cable car.

Comparison of Ventilated and Unventilated Air Temperature Measurements in Inland Dronning Maud Land on the East Antarctic Plateau

2021 ◽  
Vol 38 (12) ◽  
pp. 2061-2070
Keyword(s):  
Austral Summer ◽  
Radiative Heating ◽  
Temperature Measurements ◽  
Shortwave Radiation ◽  
Relay Station ◽  
Antarctic Plateau ◽  
Temperature Bias ◽  
Dronning Maud Land ◽  
Weak Winds ◽  
Temperature Errors

Abstract Surface temperature measurements with naturally ventilated (NV) sensors over the Antarctic Plateau are largely subject to systematic errors caused by solar radiative heating. Here we examined the radiative heating error in Dronning Maud Land on the East Antarctic Plateau using both the newly installed automatic weather stations (AWSs) at NDF and Relay Station and the existing AWSs at Relay Station and Dome Fuji. Two types of NV shields were used in these AWSs: a multiplate radiation shield and a simple cylinder-shaped shield. In austral summer, the temperature bias between the force-ventilated (FV) sensor and the NV sensor never reached zero because of continuous sunlight. The hourly mean temperature errors reached up to 8°C at noon on a sunny day with weak wind conditions. The errors increased linearly with increasing reflected shortwave radiation and decreased nonlinearly with increasing wind speed. These features were observed in both the multiplate and the cylinder-shaped shields. The magnitude of the errors of the multiplate shield was much larger than that of the cylinder-shaped shield. To quantify the radiative errors, we applied an existing correction model based on the regression approach and successfully reduced the errors by more than 70% after the correction. This indicates that we can use the corrected temperature data instead of quality controlled data, which removed warm bias during weak winds in inland Dronning Maud Land.

scholarly journals Large spatial variation in accumulation rate in Jutulstraumen ice stream, Dronning Maud Land, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 231-238 ◽  
Author(s):  
Kjetil Melvold ◽  
Jon Ove Hagen ◽  
Jean Francis Pinglot ◽  
Niels Gunuestrup
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Austral Summer ◽  
Katabatic Winds ◽  
Surface Gradient ◽  
Ice Stream ◽  
Dronning Maud Land ◽  
Temporal And Spatial ◽  
Accumulation Trend ◽  
Local Accumulation

A mass-balance programme was initiated on Jutulstraumen ice stream, western Dronning Maud Land,Antarctica, during the austral summer 1992-93. As a part of the mass-balance programme, accumulation rate was measured along the centre line of Jutulstraumen from the shelf edge up to the plateau at about 2500 m a.s.l. Accumulation distribution obtained from seven shallow firn cores and 48 slake readings is presented. The overall net accumulation trend displays a decreasing accumulation with increasing elevation and distance to coast, but on both the mesoscale and microscale there are significant variations. This is due to complex patterns of precipitation controlled by orography and redistribution by katabatic winds. The local accumulation distribution (few km scale) was found to be dependent on downslope surface gradient (aspect north, northwest), and variations up to 100% were found over distances of less than 3 km. The large variation in accumulation is important when selecting new core sites and for interpretation of temporal and spatial variations in accumulation derived from firn cores.

scholarly journals New maps of the ice thickness and subglacial topography in Dronning Maud Land, Antarctica, determined by means of airborne radio-echo sounding

1999 ◽  
Vol 29 ◽  
pp. 267-272 ◽  
Author(s):  
D. Steinhage ◽  
U. Nixdorf ◽  
U. Meyer ◽  
H. Miller
Keyword(s):  
Three Dimensional ◽  
Austral Summer ◽  
Ice Thickness ◽  
Ice Volume ◽  
Site Survey ◽  
Radio Echo Sounding ◽  
First Results ◽  
Dronning Maud Land ◽  
Subglacial Topography ◽  
Echo Sounding

AbstractSince the austral summer of 1994-95 the Alfred Wegener Institute has carried out airborne radio-echo sounding (RES) measurements in Antarctica with its newly designed RES system. Since 1995-96 an ongoing pre-site survey for an ice-coring drill site in Dronning Maud Land has been carried out as part of the European Project for Ice Goring in Antarctica. The survey covers an area of 948 000 km2, with >49 500 km of airborne RES obtained from >200 hours of flight operation flown during the period 1994-97. In this paper, first results of the airborne RES survey are graphically summarized as newly derived maps of the ice thickness and subglacial topography, as well as a three-dimensional view of surface and subglacial bed and outcrop topography, revealing a total ice volume of 1.48 x 106 km3.

scholarly journals First Results of Experimental Tests of the Newly Developed NARL Phased-Array Doppler Sodar

2008 ◽  
Vol 25 (10) ◽  
pp. 1778-1784 ◽  
Author(s):  
V. K. Anandan ◽  
M. Shravan Kumar ◽  
I. Srinivasa Rao
Keyword(s):  
Wind Speed ◽  
Phased Array ◽  
Experimental Tests ◽  
Acoustic Power ◽  
Lower Atmosphere ◽  
Physical Parameters ◽  
Atmospheric Conditions ◽  
Microwave Electronics ◽  
Doppler Sodar ◽  
First Results

Abstract A multifrequency phased-array Doppler sodar system has been installed recently at the National Atmospheric Research Laboratory (NARL) for the continuous observation of the lower atmosphere from near ground to the atmospheric boundary layer (ABL). The NARL sodar, developed in technical collaboration with the Society for Applied Microwave Electronics Engineering and Research (SAMEER), was built using piezoceramic tweeters, which are capable of generating 100-W acoustic power. In favorable atmospheric conditions, the sodar gives wind profiles up to 1 km. The performance evaluation is one of the most important aspects for quality assurance of sodar operations. This paper presents the first results of experimental observations of the NARL sodar system and its scientific validation. The NARL sodar has been validated using the simultaneous observation of another sodar system (Scintec model MFAS64). Various physical parameters of the atmosphere are derived using the results obtained from both of the systems. Comparison of simultaneous measurements by both of the sodars, located about 100 m apart, shows good agreement on wind speed, wind direction, and vertical wind variance. The correlation coefficient of more than 0.80 in wind speed and direction between the sodars shows the usefulness of the system for observing the atmosphere and deriving physical parameters below the ABL.

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