Recent geomagnetic storms observed by Macao Science Satellite-1

Geomagnetic storms are rapid disturbances of the Earth’s magnetosphere.They are related to many geophysical phenomena and have large influences on human activities.Observing and studying geomagnetic storms is thus of great significance to both scientific research and geomagnetic hazards prevention.The Macao Science Satellite-1(MSS-1)project includes two high-precision Chinese geomagnetic satellites successfully launched on May 21,2023.The main purpose of MSS-1 is to accurately measure the Earth’s magnetic field.Here,we analyze early MSS-1 geomagnetic field measurements and report observations of two recent geomagnetic storms that occurred on March 24,2024 and May 11,2024.We also calculate the related geoelectric fields as an initial step towards a quantitative assessment of geomagnetic hazards.

The dawn−dusk asymmetry in mesosphere and lower thermosphere temperature disturbances during geomagnetic storms at high latitude

Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.

Machine Learning Analysis of Impact of Western US Fires on Central US Hailstorms

Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective storms.Here,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)methods.The developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.

Seasonal Prediction of Tropical Cyclones and Storms over the Southwestern Indian Ocean Region Using the Generalized Linear Models

Tropical cyclones (TCs) and storms (TSs) are among the devastating events in the world and southwestern Indian Ocean (SWIO) in particular. The seasonal forecasting TCs and TSs for December to March (DJFM) and November to May (NM) over SWIO were conducted. Dynamic parameters including vertical wind shear, mean zonal steering wind and vorticity at 850 mb were derived from NOAA (NCEP-NCAR) reanalysis 1 wind fields. Thermodynamic parameters including monthly and daily mean Sea Surface Temperature (SST), Outgoing Longwave Radiation (OLR) and equatorial Standard Oscillation Index (SOI) were used. Three types of Poison regression models (i.e. dynamic, thermodynamic and combined models) were developed and validated using the Leave One Out Cross Validation (LOOCV). Moreover, 2 × 2 square matrix contingency tables for model verification were used. The results revealed that, the observed and cross validated DJFM and NM TCs and TSs strongly correlated with each other (p ≤ 0.02) for all model types, with correlations (r) ranging from 0.62 - 0.86 for TCs and 0.52 - 0.87 for TSs, indicating great association between these variables. Assessment of the model skill for all model types of DJFM and NM TCs and TSs frequency revealed high skill scores ranging from 38% - 70% for TCs and 26% - 72% for TSs frequency, respectively. Moreover, results indicated that the dynamic and combined models had higher skill scores than the thermodynamic models. The DJFM and NM selected predictors explained the TCs and TSs variability by the range of 0.45 - 0.65 and 0.37 - 0.66, respectively. However, verification analysis revealed that all models were adequate for predicting the seasonal TCs and TSs, with high bias values ranging from 0.85 - 0.94. Conclusively, the study calls for more studies in TCs and TSs frequency and strengths for enhancing the performance of the March to May (MAM) and December to October (OND) seasonal rainfalls in the East African (EA) and Tanzania in particular.

Statistical study on interplanetary drivers behind intense geomagnetic storms and substorms

Geomagnetic storms and substorms play a central role in both the daily life of mankind and in academic space physics.The profiles of storms,especially their initial phase morphology and the intensity of their substorms under different interplanetary conditions,have usually been ignored in previous studies.In this study,97 intense geomagnetic storms(Dstmin≤–100 nT)between 1998 and 2018 were studied statistically using the double superposed epoch analysis(DSEA)and normalized superposed epoch analysis(NSEA)methods.These storms are categorized into two types according to different interplanetary magnetic field(IMF)Bz orientations:geomagnetic storms whose IMF is northward,both upstream and downstream relative to the interplanetary shock,and geomagnetic storms whose upstream and downstream IMF is consistently southward.We further divide these two types into two subsets,by different geomagnetic storm profiles:Type Ⅰ/Type Ⅱ—one/two-step geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock;Type Ⅲ/TypeⅣ—one/two-step geomagnetic storms with southward IMF both upstream and downstream of the interplanetary shock.The results show that:(1)geomagnetic storms with northward IMF both upstream and downstream of the interplanetary shock have a clear initial phase;geomagnetic storms with southward IMF in both upstream and downstream of the interplanetary shock do not;(2)the IMF is an important controlling factor in affecting the intensity characteristics of substorms.When Bz is positive before and after the interplanetary shock arrival,the Auroral Electrojet(AE)index changes gently during the initial phase of geomagnetic storms,the median value of AE index is maintained at 500–1000 nT;(3)when Bz is negative before and after the interplanetary shock arrival,the AE index rises rapidly and reaches its maxmum value about one hour after storm sudden commencements(SSC),although the time is scaled between reference points and the maximum value of AE is usually greater than 1,000 nT,representing intense substorms;(4)for most cases,the Dst0 usually reaches its minimum at least one hour after Bz.These results are useful in improving contemporary space weather models,especially for those that address geomagnetic storms and substorms.

Analysis of the severe group dust storms in eastern part of Northwest China

Based on the available original dust storm records from 60 meteorological stations, we discussed the identification standard of severe dust storms at a single station and constructed a quite complete time series of severe group dust storms in the eastern part of Northwest China in 1954–2001. The result shows that there were 99 severe group dust storms in this region in recent 48 years. The spatial distribution indicates that the Alax Plateau, most parts of the Ordos Plateau and most parts of the Hexi Corridor are the main areas influenced by severe group dust storms. In addition, the season and the month with the most frequent severe group dust storms are spring and April, accounting for 78.8% and 41.4% of the total events respectively. During the past 48 years the lowest rate of severe group dust storms occurred in the 1990s. Compared with the other 4 decades, on the average, the duration and the affected area of severe group dust storms are relatively short and small during the 1990s. In 2000 and 2001, there were separately 4 severe group dust storms as the higher value after 1983 in the eastern part of Northwest China.

基于Lab VIEW的LEGO Mind storms轮式机器人运动轨迹实时绘制系统

本文设计了一个基于Lab VIEW平台的LEGO Mind storms轮式机器人运动轨迹实时绘制系统,本系统采用上下位机结构,使用Lab VIEW的图形化编程功能,设计了简单易用的上位机人机界面,并通过相关的函数模块化实现了对轮式机器人的控制和运动轨迹实时绘制功能。本文重点探讨了基于机器人移动方向的角度值和移动距离值,对绘制运动轨迹所需的平面坐标值的计算和机器人运动轨迹的绘制。

Ionospheric absorption at Zhongshan Station, Antarctica during magnetic storms in early May, 1998

In the paper the high latitude ionospheric absorption events, monitored by an imaging riometer at Zhongshan Station, Antarctica, are examined during magnetic storms in early May, 1998. The storm absorption at ~0639 UT on May 2 was mainly an equatorward progressing absorption event, which were associated with a strong negative bay of the magnetic H component and with a large Pc3 range pulsation. There was a time lag of about 1. 5 hours between the onset of the ionospheric disturbance and the IMF southward turning in the solar wind. The event at 2222 UT on May 2 was a typical midnight absorption spike event. The absorption region took the form of an elongated strip with the length of 100 - 150 km and the width of 30 - 40 km. The absorption during 0830 - 1200 UT on May 6 was a polar cap absorption (PCA) event,caused by intense precipitation of high-energy protons erupted after a large solar flare explosion.

Behavior of the Total Electron Content over the Arctic and Antarctic sectors during several intense geomagnetic storms

In this paper, the behavior of TEC at three stations located in the Arctic and Antarctic sectors during some intense geomagnetic storms in the period 2012-2016 is analyzed. The results show the opposite storm effects in the Arctic and Antarctic regions. Both the positive and negative TEC disturbances presented more fluctuations over the Arctic stations than over the Antarctic stations. Moreover, the positive TEC disturbances were more significant in winter. The negative disturbances were generally long-lasting,sometimes interrupted by short-duration positive disturbances. Overall, the increases and decreases in TEC can be mainly attributed to changes(i.e., increase and decreases in the O/N_2 ratio respectively) in the thermospheric composition, but prompt penetration electric field could be responsible for the initial TEC disturbances. The thermospheric circulation and the disturbance dynamo, which are maintained due to prolonged high-energy input at high latitudes, can also play important roles at the end of main phase and during recovery phase.

ANALYSIS OF AMBIENT FIELDS AND SATELLITE IMAGERY CHARACTERISTICS OF EFFECT OF BAY OF BENGAL STORMS ON LOW- LATITUDE PLATEAU

Based on the composite analysis method, 12 rainstorms triggered by Bay of Bengal storms (shortened as B-storms hereafter) across the whole province of Yunnan were studied, and some interesting results of rain and circulation characteristics influenced by the storms were obtained for low-latitude plateau. Usually, when a rainstorm weather occurs in low-latitude plateau, the B-storm center locates in the central, east or north parts of the Bay of Bengal. At the same time, the subtropical high ridge moves to 15°N– 20°N and the west ridge point moves to the Indo-china Peninsula from the South China Sea and the low-latitude plateau is controlled by southwest air streams coming from the front of the trough and the periphery of the subtropical high. The southwest low-level jet stream from the east side of the bay storm has great effect on heavy rains. On the one hand, the southwest low-level jet stream is playing the role of transporting water vapor and energy. On the other hand, the southwest low-level jet stream is helpful to keep essential dynamical condition. From the analysis of the satellite cloud imagery, it is found that mesoscale convection cloud clusters will keep growing and moving into the low-latitude plateau to cause heavy rains when a storm forms in the Bay of Bengal.

The diurnal transport of atmospheric water vapor during major dust storms on Mars based on the Mars Climate Database,version 5.3

In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides.This process,when coupled with deep convection,could be an important part of the short-term atmospheric dynamics of water escape.However,the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated.In this work,we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide(DW1)at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database(MCD)5.3,a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well.We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years(MYs)24 to 32.Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1.The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons.During regional dust storms,the tidal transport induces only limited diurnal motion of the water vapor.However,the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid-to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm.The tidal transport process during these two global dust storms can induce opposite effects on water escape.

Main Characteristics of Dust Storms and Their Radiative Impacts: With a Focus on Tajikistan

known aridity of the region is a major factor in promoting numerous dust storms. They have many diverse impacts on the environment and the climate of the region. The classification of dust storms and synoptic conditions related to their formation in Central Asia are discussed in the content of their diverse impact. We address dust optical properties that are representative of the region. Dust storms significantly reduce visibly and pose a human health threads. They also cause a significant impact on the radiative regime. As a result, dust storms may cause a decrease in temperature during daytime of up to 16℃ and an increase in temperature during night time from up to 7℃ compared to a clear day.

Thermospheric Density Anomaly in the Polar Cap Region During Geomagnetic Storms

The heating of the ionosphere-thermosphere system at high latitudes is a rather common phenomenon in the space climate.During geomagnetic storm time, Joule-heating enhances at high altitudes.The heating generates atmospheric upwelling causing large changes in thermospheric composition and hence in the total mass density.The CHAMP satellite with its complementary payload and long-duration mission provides an excellent dataset for studying the storm-related heating of the upper atmosphere.Based on the four-year accelerometer measurements,density enhancements in polar cap region are observed

Statistical study on great geomagnetic storms during solar cycle 23

Characteristics of great geomagnetic storms during solar cycle 23 were statistically investigated. Firstly, we focused on the uniqueness of solar cycle 23 by analyzing both the great storm number and sunspot number from 1957 to 2008. It was found that the relationship between the sunspot number and great storm number weakened as the activity of the storms strengthened. There was no obvious relationship between the annual sunspot number and great storm number with Dst≤-300 nT. Secondly, we studied the relationship between the peak Dst and peak Bz in detail. It was found that the condition Bz〈-10 nT is not necessary for storms with Dst≤-100 nT, but seems necessary for storms with Dst≤-150 nT. The duration for Bz≤-10 nT has no direct relationship with the giant storm. The correlation coefficient between the Dst peak and Bz peak for the 89 storms studied is 0.81. After removing the effect of solar wind dynamic pressure on the Dst peak, we obtained a better correlation coefficient of 0.86. We also found the difference between the Dst peak and the corrected Dst peak was proportional to the Dst peak.

Salt Desert and Saline-Ackaline Mixed Dust Storms:An Ignored Issure for Global Climate Change

Salt desert,saline-alkaline dust storm and saline-alkaline mixed dust storm are significant but ignored problems for a long time.After many years of observations and researches,the author believes that salt desert,saline-alkaline dust

Saline-Alkali(Mixed) Dust Storms and Their Main Generation Mechanism

The exposed surface of the dry salt lake basin contains a large number of extremely fine lightweight saline-alkali(mixed)dust and clay dust.It is extremely easy to dust and since saline-alkali lake is low-lying and its temperature

A Linear Diagnostic Equation for the Nonhydrostatic Vertical Motion W in Severe Storms

A linear diagnostic equation for the nonhydrostatic vertical motion W in severe storms is derived in the Cartesian-earth-spherical coordinates. This W diagnostic equation reveals explicitly how forcing factors work together to exert influence on the nonhydrostatic vertical motion in severe storms. If high-resolution global data are available in Cartesian coordinates with guaranteed quality, the Lax-Crank-Nicolson scheme and the Thomas algorithm might provide a promising numerical solution of this diagnostic equation. As a result, quantitative analyses are expected for the evolution mechanisms of severe storms.

A Four-Dimensional Variational System for Skillful Operational Prediction of Convective Storms

Forecasting convective storms using NWP models is an important goal and a highly active area of ongoing research. Skillful and reliable NWP of convective storms could allow for severe weather warnings with longer lead times, as opera- tional forecasters begin to incorporate convective-scale fore- casts into severe weather forecast operations （Stensrud et al., 2009, 2013）. This would then provide vulnerable individuals and industries with more time to seek shelter and/or mitigate the impact of severe weather hazards.

Correlating the interplanetary factors to distinguish extreme and major geomagnetic storms

We investigate the correlation between Disturbance Storm Time(Dst)characteristics and solar wind conditions for the main phase of geomagnetic storms,seeking possible factors that distinguish extreme storms(minimum Dst<−250 nT)and major storms(minimum Dst<−100 nT).In our analysis of 170 storms,there is a marked correlation between the average rate of change of Dst during a storm’s main phase(ΔDst/Δt)and the storm’s minimum Dst,indicating a fasterΔDst/Δt as storm intensity increases.Extreme events add a new regime toΔDst/Δt,the hourly time derivative of Dst(dDst/dt),and sustained periods of large amplitudes for southward interplanetary magnetic field Bz and solar wind convection electric field Ey.We find that Ey is a less efficient driver of dDst/dt for extreme storms compared to major storms,even after incorporating the effects of solar wind pressure and ring current decay.When minimum Dst is correlated with minimum Bz,we observe a similar divergence,with extreme storms tending to have more negative Dst than the trend predicted on the basis of major storms.Our results enable further improvements in existing models for storm predictions,including extreme events,based on interplanetary measurements.

Possibility of Excitation of Magnetospheric Modes by Strong Geomagnetic Storms

In this paper, we advance the possibility of strong geomagnetic storms (called sometimes super geomagnetic storms) exciting oscillation modes of the magnetosphere with some defined periods. To determine this possibility, we analyze the whole period of duration of some particularly strong geomagnetic storms through the Fourier transformation. We obtain some results on the strongest geomagnetic storm of the time series, the one from March 1989.