Kannemadugu, Hareef baba shaebRanganathan, KavipriyaGharai, BiswadipSeshasai, M. V. R....
14页
查看更多>>摘要：Integrated Water Vapor (IWV) is an important parameter that influences a wide variety of atmospheric processes such as the earth's radiation budget, cloud formation, and the hydrological cycle. IWV derived from 18 GNSSbased GPS locations in India at hourly intervals for a period of one year are analyzed for diurnal, seasonal, and spatial variability. Diurnal variation in IWV anomaly range from -0.25 - 0.3 cm with a peak in the afternoon hours and has seasonal dependence at the majority of the stations. Seasonal variation of IWV suggests a maximum in summer monsoon in the range 3.88-6.29 cm and a minimum in winter in the range 0.94-3.76 cm. This is due to the transport of the high amount of moisture from the Arabian Sea during the summer monsoon, and in winter low temperature (low wind speeds) inhibits the moisture convection (advection). IWV displays significant spatial variability at inter-and intra-seasonal timescales. Evaluation of ECMWF reanalysis (ERA5) IWV using GPS IWV, carried out first time over India using hourly comparison data sets, reveals a high correlation coefficient within the range 0.93-0.99, indicating its ability to capture the variation in IWV very well. RMSE is observed to be in the range 0.21-0.38 cm and mean RMSE is observed to be 0.28 +/- 0.04 cm. Bias (GPS IWV - ERA-5 IWV) is observed to be in the range -0.49 to 0.24 cm, and the mean bias is observed to be - 0.15 +/- 0.21 cm. GPS IWV registers a sharp rise before the rainfall event and indicates a strong correlation between them. Evaluation of ERA-5 IWV data suggests its great application prospects in the tropical Indian region, including its use in the improvement of rainfall prediction in the absence of a dense GPS network.
查看更多>>摘要：Forecasting of solar flares remains a challenge due to the limited understanding of the underlying physical processes of these events, in particular magnetic reconnection. Studies have indicated that changes to the photospheric magnetic fields associated with magnetic reconnection - particularly in relation to the field helicity - occur during solar flare events. This study utilized data from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) and SpaceWeather HMI Active Region Patches (SHARPs) to analyze full vector-field component data of the photospheric magnetic field during solar flare events within a near decade long HMI dataset. Analysis of the data was used to identify and compare the trends of differing flare classes for varying time intervals leading up to an event, as well as the trends of flares that occur with and without a precursor flare, in order to discern signatures of the physical mechanisms involved. The data suggests that active regions that produce flares with precursors are continuing to evolve and appreciably more complex than those that produce a flare without a precursor. Additionally, precursor flares were found to enhance the shear across an active region, helping set up the conditions necessary for a larger solar flare to occur. Ultimately none of the SHARP parameters showed a distinct signature of magnetic reconnection.
Krasnov, V. M.Kuleshov, Y., VKoristin, A. A.Drobzheva, Ya, V...
9页
查看更多>>摘要：Exact solutions of Maxwell's equations and the equation of motion of charged particles under the action of a radio wave (for frequencies exceeding the gyro-frequency) and the Earth's magnetic field shows the occurrence of an oscillating polarization current. Using the example of estimates of the HF radio wave amplitude during the operation of the EISCAT high power transmitter, it is shown that the oscillating polarization current can lead to significant losses of radio wave energy. This current allows us to explain the reasons for the efficiency of the high power transmitter on November 6, 2010 (a strong perturbation of the electron density and temperature was observed) and the absence of the effect on March 4, 2011. In the first case, most of the HF radio wave energy reached the height of the reflection point in the F-layer region, and led to noticeable changes in the electron density and temperature. In the second case, most of the HF radio wave energy losses could occur at altitudes below the F-layer due to the appearance of a significant oscillating polarization current, and therefore the HF radio wave could not have a noticeable effect on the F-layer.
查看更多>>摘要：The present analysis reported the lee wave interpretation on Arsia Mons Elongated Cloud (AMEC) that used to appear over the lee side of the Arsia Mons. The present work also reported the wavelength, the cloud's height, and wind speed of the observed lee wave structure. The estimated wind speed is 86 +/- 4.9 m/s, with a wavelength of 60 +/- 0.3 km at an altitude of 55 +/- 7 km. This is the largest lee wave structure that appears during the dust storm season (Ls = 230 to Ls = 300) and strongly contributes to the planet's Albedo level. Calculated TOA reflectance varies from 0.05 to 0.15 for the blue channel and 0.02 to 0.09 for the red channel. Estimated AOD ranges from 1.8 (red channel) to 1.5 (blue channel), indicating the contribution of dust and water ice crystal. The estimated angstrom exponent (alpha) value signifies coarse mode particle presence in the cloud with an effective radius of 3.2 mu m. The presence of water ice crystal contributes to the albedo level's increment to 0.8 and signifies the formation temperature for AMEC to be around 190 K.
查看更多>>摘要：This paper presents the statistical analysis of several parameters associated with the electric field generated by negative cloud-to-ground (CG) lightning flashes recorded in the Bogota savannah (central province of Colombia), including a comparison with other regions. In this way, this is the first study in Colombia where eleven parameters of the electric field and two more related to the electric field derivative are analyzed in detail. From a measuring campaign carried out during the second semester of 2016, 306 negative cloud-to-ground lightning flashes containing the same number of first return strokes (FRS) and 483 subsequent return strokes (SRS) had been analyzed. These return strokes occurred in the range from 3 to 250 km from the measuring station, in such a way that the waveforms analyzed have static components, radiated components or a combination of both. At first, a total of 64.7% of negative CG flashes were categorized as multiple-stroke flashes, the average multiplicity was 2.6 strokes/flash and the maximum value reported was 13 strokes. For the first and subsequent return strokes analyzed in Colombia, the arithmetic mean (AM) of the initial electric field peak normalized to 100 km (Ep_(N)) were 27.6 V/m and 12.4 V/m, respectively. On the other hand, the average of the peak value of the electric field derivative (dE/dt)(p) was 5.9 V/m/mu s for FRS and 3.6 V/m/mu s for SRS. These results are similar to those observed in Florida, Germany, Sweden, Japan, Sri Lanka and Malaysia, where the Ep_(N) and the (dE/dt)(p) for FRS are larger than those for SRS. Furthermore, as reported in Malaysia and other tropical regions, several electric field parameters in Colombia are affected by the geographical location, the distance with respect to the measuring system and the propagation medium. The above was more evident for some temporal parameters such as zero-to-peak rise time, the 10-90% transition duration, the slow front duration and the fast front duration. After comparing with previous data related to natural and rocket-triggered lightnings measured in different regions (tropical, subtropical and temperate latitudes), additional differences were also observed.
查看更多>>摘要：This paper investigates the complexity of soil radon time series (RTS) recorded from March 2017 to April 2018 in Pakistan via RTM 1688-2 monitor, in direct linkage to parallel series of temperature, relative humidity, and pressure. Several complexity measures are employed. The normalized Lempel Ziv Complexity (LZC) of the complete RTS is 0.30 and 0.14, 0.22, and 0.14 for the complete time series of temperature, relative humidity and pressure respectively. LZC ranges between 0.3 and 0.5 for RTS and between 0.1 and 0.3 for temperature (T), relative humidity (RH) and pressure (P). Hurst exponent (HE) values via rescaled range (R/S) analysis show an inverse relationship with LZC. HE ranges between 0.60 < HE < 0.98 for RTS, 0.60 < HE < 0.92 for T series, 0.61 < HE < 0.93 for RH series, and 0.87 < HE < 0.98 for P series. Permutation Entropy (PE) is 1.7809 for complete RTS with a minimum of 1.7668 in August 2018. Highest value of Sample Entropy (SE) is 1.3716 for February 2018. The highest symbolic Normalized Corrected Shannon Entropy (NCSE) value is found in January 2018 with a value of 0.7864. Finally, the Fractal Dimensions varied significantly for calculation with the Sevcik's, Higuchi's and Katz's methods. Common dates of below threshold areas are reported. The different aspects of the derived results are discussed.
NSTL
Elsevier