Evaluations of the Characteristics of the Tropo-Strato-Mesopause Height and Temperature Variability over Bahir Dar, Ethiopia (11.60 N, 37.30 E) Using SABER

The height profile of atmospheric temperature data between 12 km and 100 km was obtained from SABER/TIMED satellite instruments during the year 2016 and used to characterize the three atmospheric pauses temporal variability of height and temperature over Bahir Dar, Ethiopia (11.60 N, 37.30 E). The daily, monthly, and frequency distributions of tropopause-stratopause-mesopause height and temperature are investigated. From the frequency distribution, we had found that of the tropopause-stratopause-mesopause height 17 km, 48 km, and 98 km with the corresponding temperature 192 K, 268 K, and 148 K. The decrement (cooling) trend lines of tropopause height 0.7 K/year and its corresponding tropopause increment temperature has been ~1.5 K/year. The stratopause and mesopause trend lines of height are insignificant and the corresponding decrement (cooling) temperatures are ~3 K/year and ~13 K/year respectively. The mean monthly maximum heights of tropopause 19 km in May with a corresponding maximum temperature of 201 K in September. The maximum stratopause height 49.5 km in February and July and its temperature 268 K and 267 K in February and April respectively. The maximum mesopause height 98 km, 95 km, 97 km in March, Jun, and November respectively, and its maximum temperature 196 K and 198 K in January and July respectively

Error Modeling Radar Rainfall Estimation Through Incorporating Rain Gauge Data Over Upper Blue Nile Basin, Ethiopia

Accurate and precise measurements of rainfall from weather radar reflectivity data is essential to supplement the limited characterization of spatial and temporal measurements provided by insufficient network and density of rain gauges. While weather radar has high spatial and temporal resolution, it contaminated with various sources of errors due to the conversion of reflectivity to rain rate and the projectile rainfall motion. Error modeling improvement with the application of projectile rainfall motion correction is essential to improve the radar data. However, stile is not well documented for over the world as well as Ethiopia. Therefore, the aim of this study was to generate an error model for weather radar rainfall estimation by incorporating gauge rainfall data over upper Blue Nile basin, Ethiopia. Projectile rainfall motion correction is considered on the data of reflectivity and rain rate to determine empirical error model parameter values. The model parameter values are found, multiplicative factor (a) was 55, the exponent factor (b) was 1.12, standard deviation of proportional error was 0.08 and standard deviation of random error was 0.07. The value of the total error varied from -0.45 to 1.16 mm and the domain of proportional error was greater than random error. After applying the projectile rainfall motion correction, the total error is reduced by 12%. In general, the assumption of projectile method is quite useful for improving the radar data over upper Blue Nile basin in Ethiopia as well as over the world. Hence, we wish to extend this method for other regions

NN‐MLT Model Prediction for Low‐Latitude Region Based on Artificial Neural Network and Long‐Term SABER Observations

Abstract The low‐latitude mesosphere and lower thermosphere (MLT) regions are distinct and, highly turbulent transition zones in Earth's atmosphere. The scarcity of reliable measurements makes continuous monitoring of these areas challenging. Therefore, the necessity for studies focused on the MLT region cannot be overstated, as they are essential for developing effective models that meet the accuracy requirements of satellite‐based observations. The neural networks NN‐MLT model, developed using 15 years of Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics/satellite, equipped with Broadband Emission Radiometry (SABER) observed temperature data spanning from January 2006 to December 2020, employs neural network techniques. The data set was split, with 90% used for training and the remaining 10% allocated for prediction. The model's validation was tested with two other partitions (80(20) and 70(30)). The 90(10) partition, exhibiting a high correlation coefficient (R), low standard deviation (σ), and low root mean square error (RMSE), demonstrated the model's good performance. As clearly shown from statistical metrics (R, RMSE, mean, and σ) at three specific altitude levels (60, 75, and 90 km), the NN‐MLT model's performance aligns closely with the empirical model (NRLMSISE2‐0) and SABER observations. The NN‐MLT model displays a high R (0.74) and low RMSE (4.35 K) at 60 km, indicating its effective performance compared to the other two heights of 75 and 90 km. The NN‐MLT model's spatiotemporal variability in MLT temperature prediction agrees well with the SABER data at all altitudes, particularly at 60 km. While the NN‐MLT model accurately captures the seasonal variations of MLT temperature, the analysis leads to the conclusion that it consistently outperforms the empirical model and aligns closely with observations

Temperature Anomalies Associated with Sudden Stratospheric Warming, Observed Above the Tropical Site of Gadanki (13.5°N, 79.2°E) with a Rayleigh Lidar

International audienceA quasi continuous Rayleigh lidar measurements of middle atmospheric temperature (30-70km region) have been carried out from Gadanki (13.5 N, 79.2 E), India between June, 1998 and April, 1999. Summer temperature showed a smooth and regular variation with altitudes and reasonably good agreement with MSISE-90 model atmosphere. By, contrast winter temperatures are perturbed continuously by planetary waves, as long as prevailing winds are westerlies, from October to March. Pronounced stratospheric cooling and a minor stratospheric warming events were observed during this winter period. The stratopause height and temperature vary considerably during the evolution of this phenomenon. Spectral analysis of the data reveals the presence of a 16-day wave interpreted as a free Rossby wave, another wave with large perturbations having periods of 23 to 35 days. Amplitude and Phases of theses waves exhibits a peculiar structure " quiet atmospheric layer " corresponds to the regions of minimum variability of Quasi-Stationary planetary wave no. 2 of the CIRA-86 model. The thermal structure of tropical stratosphere of northern hemisphere seems to be influenced by the dynamics of the winter time stratospheric warmings at the mid/high-latitudes. The stratospheric warming event over Gadanki appeared to be linked to warming event over the mid-latitude region. Our analysis partially strengthens the point of " propagation of 16-day planetary waves over equatorial stratosphere invades the mid-latitudes from the tropics during the evolution of Stratospheric Sudden Warming "

Tropical stratopause features - Rayleigh lidar observations over Gadanki (13.5°N, 79.2°E), India

International audienceThe characteristics of straggle feature "Double stratopause" observed in temperature profiles using Rayleigh lidar at National Atmospheric Research Laboratary (NARL), Gadanki (13.5°N, 79.2°E), India is presented in this paper. Out of 216 nights of observations made during March 1998-April 2001, the double stratopause is observed for 122 days (~56.5 %). The two stratopause peaks are found to be separated by ~2-10 km. Applying third order polynomial fit to the mean temperature profiles provided the quantification on peak and trough stratopause heights and temperatures. The monthly percentages of occurrence of double stratopause show peaks in June and September with weak seasonal dependence. The splitting in stratopause is considered in terms of gravity wave breaking due to Kelvin Helmholtz instability. There appeared to be a sudden increase in gravity wave potential energy in stratopause region during the presence of its split and also observed a maximum speed in wind, derived from NCEP reanalysis data

Nocturnal temperature changes over Tropics during CAWSES -III campaign: Comparison with numerical models and satellite data

International audienceIn the frame of the third CAWSES tidal campaigns in June-August 2007, lidar and satellite data were collected and compared with numerical models. Continuous nocturnal middle atmospheric temperature measurements performed with a Rayleigh lidar located at La Reunion Island (20.8°S-55.5°E) were obtained for three continuous nights. The results clearly show the presence of tidal components with a downward phase propagation. Comparisons with SABER satellite data show good agreement on tidal amplitude, however some differences on the structures are reported at some places probably due to the zonal nature of the retrieval provided by the SABER data. The observed tidal components are compared with two different numerical models such as the 2D Global Scale Wave Model, and the 3D-GCM LMDz-REPROBUS. Both models reveal good agreement with temperature lidar patterns, while simulated tidal amplitude are smaller by a factor of around two

Lidar observations of middle atmosphere temperature variability over low latitude

50-57In this paper, 246 Rayleigh lidar observations covering the altitude range of stratosphere and mesosphere collected during the period March 1998- December 2001 (37 months) using Indo-Japanese Lidar at National MST Radar Faculty (NMRF), Gadanki (13.8°N, 79.2°E), India, are presented. The atmospheric density profiles were derived. Using the limited database, a climatological structure of temperature over a tropical site giving seasonal variations of upper stratosphere and mesospheric region is also presented. It has been observed over Gadanki, that the stratopause is quite broad and occurred in the range of 43-58 km with the temperature maximum observed in winter and equinox periods. A semi-annual variation is seen clearly around 70 km with maxima at May/June and Dec/Jan. Mesospheric temperature shows strong inversion very often. The average climatology over 37 months period is found to compare well with a reference atmosphere model (MSISE 90). The observed temperature is, in general, colder throughout the year in the 30-45 km range and warmer in summer at 70-80 km as compared to the model derived values. The present study suggests that the 45-55 km region is less affected by temperature variability, which is well suited for the detection of possible temperature trend

Lidar observations of middle atmosphere temperature variability over low latitude

In this paper, 246 Rayleigh lidar observations covering the altitude range of stratosphere and mesosphere collected during the period March 1998 - December 2001 (37 months) using Indo-Japanese Lidar at National MST Radar Faculty (NMRF), Gadanki (13.8°N, 79.2°E), India. are presented. The atmospheric density profiles were derived. Using the limited database, a climatological structure of temperature over a tropical site giving seasonal variations of upper stratosphere and mesospheric region is also presented. It has been observed over Gadanki, that the stratopause is quite broad and occurred in the range of 43-58 km with the temperature maximum observed in winter and equinox periods. A semi-annual variation is seen clearly around 70 km with maxima at May/June and Dec/Jan. Mesospheric temperature shows strong inversion very often. The average climatology over 37 months period is found to compare well with a reference atmosphere model (MSISE 90). The observed temperature is, in general, colder throughout the year in the 30-45 km range and warmer in summer at 70-80 km as compared to the model derived values. The present study suggests that the 45-55 km region is less affected by temperature variability, which is well suited for the detection of possible temperature trends