Spatial and Temporal Variation of the Near-Surface Wind Environment in the Sahara Desert, North Africa

The Sahara Desert is the largest source of dust on Earth, and has a significant impact on global atmospheric changes. Wind is the main dynamic factor controlling the transport and intensity of dust in the Sahara Desert. This study comprehensively analyzed the spatial and temporal variation in the wind regime of the Sahara Desert from 1980 to 2019 using data from 17 meteorological stations to improve awareness of global atmospheric changes and the intensity of regional aeolian activities. All wind speed parameters decreased from northwest to southeast. While there were significant differences in the trends of temporal variation in wind speed among the different regions, there was an overall decreasing trend across the Sahara Desert, with an average wind speed of 0.09 m s−1 10 a−1. This decrease was closely related to wind frequency. The easterly, westerly, and northerly winds dominated, with more complex wind direction in the northern region. Seasonal differences in wind direction were observed in all regions. The wind direction frequency of wind speeds >6 m s−1 exceeded those with wind speeds <6 m s−1 in the western and northern regions, whereas other regions showed an opposite pattern. The highest drift potential (DP) and resultant drift potential (RDP) were found in the western and northern regions, and during spring and winter. There was a trend of decreasing annual variation in DP and RDP in all regions. The directional variability (RDP/DP) indicated mostly intermediate and high variability in wind direction. Resultant drift direction (RDD) indicated that a mainly southwest wind direction. No apparent trends in temporal variation in RDD and RDP/DP were observed. Total DP was strongly influenced by DP and the magnitude and frequency of strong winds in the prevailing wind direction. No strong correlation between wind regimes and dune types was observed in this desert, indicating the complexity of factors affecting dune morphology.

The Storage of Antecedent Precipitation and Air Temperature Signals in Soil Temperature over China

Soil temperature (ST) is one of the key variables in land-atmosphere interactions. The response of ST to atmospheric changes and subsequent influence of ST on atmosphere can be recognized as the processes of signals propagation. Understanding the storing and releasing of atmosphere signals in ST favors the improvement of climate prediction and weather forecast. However the current understanding of the lagging response of ST to atmospheric changes is very insufficient. The analysis based on observation shows that both the storage of air temperature signals in deep ST even after four months and the storage of precipitation signals in shallow ST after one month are widespread phenomena in China. Air temperature signals at 2m can propagate to the soil depths of 160 cm and 320 cm after 1 month and 2 months, respectively. The storage of antecedent air temperature and precipitation signals in ST is slightly weaker and stronger during April to September, respectively, which is related to more precipitation during growing season. The precipitation signals in ST rapidly weaken after 2 months. Moreover, the effects of accumulated precipitation and air temperature on the signal storage in ST have significant monthly variations and vary linearly with soil depth and latitude. The storage of antecedent air temperature or precipitation signals in ST exhibits an obvious decadal variation with a period of more than 50 years, and it may be resulted from the modulation of the global climate patterns which largely affect local air temperature and precipitation.

Agreement of rebound and applanation tonometry intraocular pressure measurements during atmospheric pressure change

This study investigated the agreement of intraocular pressure measurements using rebound tonometry and applanation tonometry in response to atmospheric changes in a hyperbaric chamber. Twelve eyes of 12 healthy subjects were included in this prospective, comparative, single-masked study. Intraocular pressure measurements were performed by rebound tonometry followed by applanation tonometry in a multiplace hyperbaric chamber at 1 Bar, followed by 2, 3 and 4 Bar during compression and again at 3 and 2 Bar during decompression. Mean differences between rebound and applanation intraocular pressure measurements were 1.6, 1.7, and 2.1 mmHg at 2, 3, and 4 Bar respectively during compression and 2.6 and 2.2 mmHg at 3 and 2 Bar during decompression. Lower limits of agreement ranged from -3.7 to -5.9 mmHg and upper limits ranged from -0.3 to 1.9 mmHg. Multivariate analysis showed that the differences between rebound and applanation intraocular pressure measurements were independent of atmospheric pressure changes (p = 0.79). Intraocular pressure measured by rebound tonometry shows a systematic difference compared to intraocular measured by applanation tonometry, but this difference is not influenced by changes of atmospheric pressure up to 4 Bar in a hyperbaric chamber. Agreement in magnitude of change between devices suggests rebound tonometry is viable for assessing intraocular pressure during atmospheric changes. Future studies should be designed in consideration of expected differences in IOP values provided by the two devices.

Lightning Behaviour during the COVID-19 Pandemic

Background COVID-19 has drastically dampened human activities since early 2020. Studies have shown that this has resulted in changes in air temperature and humidity. Since lightning activities are dependent on air temperature and humidity, this study is conducted to evaluate the correlation between the intensity of lightning activities with the atmospheric changes, and investigates the changes, in lightning activities due to atmospheric changes during the COVID-19 pandemic. Methods The hypothesis was tested through a t-test and Pearson’s correlation study. The variation trend of lightning strikes count (LSC) in Europe and Oceania during the five months COVID-19 lockdown period (March – July) compared to the same period in the previous five years from 2015 to 2019 is investigated. Results Statistical analysis shows the LSC in Europe and Oceania during the lockdown period dropped significantly by more than 50% and 44% respectively compared to the same period in previous five years. Furthermore, LSC was found to be positively correlated with air temperature and relative humidity in Europe. However, in Oceania, LSC seems to be only positively correlated with air temperature but negatively correlated with relative humidity. Conclusions This study seems to suggest that lightning activities have significantly changed during this pandemic due to reduction in human activities.

Lightning Behaviour during the COVID-19 Pandemic

Background COVID-19 has drastically dampened human activities since early 2020. Studies have shown that this has resulted in changes in air temperature and humidity. Since lightning activities are dependent on air temperature and humidity, this study is conducted to evaluate the correlation between the intensity of lightning activities with the atmospheric changes, and investigates the changes, in lightning activities due to atmospheric changes during the COVID-19 pandemic. Methods The hypothesis was tested through a t-test and Pearson’s correlation study. The variation trend of lightning strikes count (LSC) in Europe and Oceania during the five months COVID-19 lockdown period (March – July) compared to the same period in the previous five years from 2015 to 2019 is investigated. Results Statistical analysis shows the LSC in Europe and Oceania during the lockdown period dropped significantly by more than 50% and 44% respectively compared to the same period in previous five years. Furthermore, LSC was found to be positively correlated with air temperature and relative humidity in Europe. However, in Oceania, LSC seems to be only positively correlated with air temperature but negatively correlated with relative humidity. Conclusions This study seems to suggest that lightning activities have significantly changed during this pandemic due to reduction in human activities.

Awareness for Atmospheres

In this essay I reflect on the meaning of atmospheres while the human world has been overwhelmed by a respiratory disease. In an auto-ethnographic gesture I reflect different ways of sensing and becoming sensitive to the atmospheric changes in my home during self-isolation. This self-questioning is directly related to the conceptualisation of air in view of its potential risk of carrying infectious virus particles. The air we breathe is currently stylised as a cloud on the micro level of aerosols, which gives reason to think anew about the status of the atmospheric with regard to our being in the world. Through combining philosophical reflection with aesthetic practice, I explore how an attunement towards the ways air flows through our habitats can open a new perspective on processes of subjectivation in a time of ongoing crisis. I argue that becoming sensitive towards air flow not only heightens our sensitivity for the affectivity of atmospheric processes but also for the different registers of our experience able to capture these effects.

Atmospheric Changes and Ozone Increase in Mexico City during 2020 Lockdown Period

Atmospheric pollutant (NO2, SO2, CO, O3 and PM2.5) variations during the COVID-19 pandemic (during 2020) have been studied from Mexico City in Central America. Meteorological factors (i.e) rainfall, temperature along with relative humidity played an important role in increasing the photochemical reaction for the formation of O3 and PM2.5. Concentration pattern of O3 and PM2.5 were higher in all the stations in spite of the reduced primary pollutants. However, higher level of O3 and PM2.5 during the lockdown period in 2020 is mainly due to the air-mass exchange which happened through the broader channel in the north (Tenango del Aire Pass) and in the southeast (Cuautla-Cuernavaca valley). The higher values of particulate matter are compensated by domestic heating (“Quédate en Casa”/ Stay at Home), whereas the increase of O3 is supported by the higher solar radiation and household activities (both indoor/ outdoor). Monitoring stations (BJ, GAM, UAM, SFE) in Mexico City indicate that the level of pollutants (except GAM) were within the WHO guidelines. Comparison of pollutants with other countries indicate a spike in NO2, O3 and PM2.5 levels. Overall results indicate that the anthropogenic activities which is influenced by the meteorological parameters has affected the air quality in Mexico City and it persisted during the lockdown period.