 View of Johannesburg, Image: Eva Melusine Thieme, OP Source: https://www.goodthingsguy.com/opinion/johannesburg-living-worlds-dangerous-city/ Over the past few decades there has been a growing interest in investigating the link between weather and various types of crimes. However, most research in this area has produced inconsistent and often paradoxical results. For instance, a few studies have found no apparent seasonal fluctuations in crime. Others have found a rise in crimes during either colder winter months or warmer summer months. However, very little is known about how the amplitude and spatial distribution of criminal activity in South Africa is affected by climatic conditions. A study was performed to determine a link between criminal activity and climate in the country's capital city known as Tshwane. The aim was to investigate whether there was any correlation between the frequency in crime rate and extreme weather conditions, using temperature and rainfall as proxy. In other words: do extremely hot days or high-rainfall days experience higher or lower rates of violent, property or sexual crime? The spatial distribution of different crime types and extreme weather events were also analysed. Simply put, does crime occur in different places on extremely cold days than it does on really hot ones?
The results suggest a strong association between temperature and criminal activity, with an increase in crime rate in step with a temperature rise. There’s a less significant association between rainfall and crime. The spatial distributions of all types of crime are found to differ significantly depending on the type of weather extreme observed. These results could help law enforcement agencies better understand how weather affects crime patterns in South Africa’s urban areas and develop and implement appropriate crime prevention measures. The notion that there’s a relationship between criminal activity and climate is nothing new. Over a century ago, Belgian sociologist and scholar Adolphe Quételet observed that crimes against people reach a maximum during the warmer summer months, while crimes against property reached a peak during winter. Later, he developed the temperature-aggression theory, which provides a psychological explanation for the increase in crime during warmer months. It suggests that warmer temperatures will lead to an increase in an individual’s frustration and discomfort levels and so increase the likelihood of aggression. This could in turn result in interpersonal crimes such as assault. In the case of the Tshwane study, statistical analysis was performed to find any relationship between extreme weather conditions and crime in the nation’s capital. Climate data for the city was obtained from the South African Weather Service over a 5-year period from September 2001 to the end of August 2006. Daily average temperatures were computed before extracting the ten hottest for each year of the five years resulting in a dataset of 50 days. The process was repeated for low-temperature days, high-rainfall days, no-rainfall days and random-rainfall days. Crime data for the same period were also retrieved from the South African Police Services’ Crime and Information Analysis Centre. The data included the geographical location of each crime; the date and time of day that each crime was committed; and the specific type of crime committed. A total of 1,361,220 crimes were reported in the five-year period across 32 different categories. All crime was then categorised into either violent, sexual or property crimes before calculating a count of crime per type per day. Next, a recently developed method called the spatial point pattern test was used to determine whether the spatial distribution of crime on the three types of days (very hot, very cold and rainy) changes. That is, does the spatial patterning of crime in Tshwane change depending on certain rainfall and temperature conditions? The findings demonstrate that the amount of violent, sexual and property crime in the city of Tshwane is significantly affected by temperature and, to a lesser extent, rainfall. The magnitude of violent, sexual and property crime was higher on hot days compared to cold or random temperature days. Violent crimes increased by 50% on hot days compared to very cold days. Sexual crimes increased by 41% and property crime by 12%. Violent and sexual crimes in Tshwane also decreased on high-rainfall days. Surprisingly, property crime was found to increase slightly on heavy rainfall days, though only by 2%. Second, the spatial distribution of violent and property crime was found to differ on days by temperature and rainfall. There is a considerable change in the way that particularly violent and property crime is spatially distributed in Tshwane depending on the weather conditions. More research is needed to confirm these findings and to determine if the results can be generalised to other urban areas in South Africa. Our findings can be used to identify communities that are more prone to crime under certain meteorological conditions and allow stakeholders to target these neighbourhoods and plan interventions. It also allows stakeholders to adequately develop and implement suitable intervention practices in similar at-risk neighbourhoods. For the police and others responsible for specifically addressing long-term solutions to crime, crime pattern analysis can utilise the understanding of how weather events influence crime patterning and provide measures to take appropriate action. Article Sources: Breetzke, G. (2018, August 7). When temperatures rise, so do crime rates: evidence from South Africa. The Conversation. Retrieved August 31, 2018, from https://theconversation.com/when-temperatures-rise-so-do-crime-rates-evidence-from-south-africa-100850 Melusine Thieme, E. (2017, July 13). Johannesburg. Living in the world’s most dangerous city. Good Things Guy. Retrieved August 31, 2018, from https://www.goodthingsguy.com/opinion/johannesburg-living-worlds-dangerous-city/ To learn more about other climate-related stories occurring across Africa, be sure to click here! © 2018 Oceanographer Daneeja Mawren
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 A National Weather Service meteorologist in Norman, Oklahoma, tracking a super cell tornado outbreak (NOAA). Source : http://www.noaa.gov/explainers/improving-weather-forecasts Weather forecasting is an imperfect science. Through decades of research, meteorologists have come up with tools that allow us to fairly accurately predict weather in the short term using numerical modeling and forecast analysis. Beyond the scope of about a week however, the certainty in these forecasts drops off significantly. This is because weather is based on an infinitely complex and constantly changing system, with a little bit of chaos thrown in for fun.
There are many steps involved in weather forecasting. Firstly, a global snapshot of the atmosphere is captured at a given time and mapped onto a 3-D grid of points that extend over the entire globe from the surface to the stratosphere. Using a powerful computer and a numerical model that describes the behaviour of the atmosphere incorporated with physics equations, this snapshot is therefore pushed forward in time to produce terabytes of raw forecast data. These data are then interpreted by human forecasters which turn them into a meaningful forecast broadcasted to the public. Forecasting the weather is challenging as we attempt to predict something that is inherently unpredictable. Since the atmosphere is a chaotic system, any small change at one location will cause remarkable consequences elsewhere over time, which was analogised as the so-called butterfly effect. Therefore, any error that develops in the forecast will grow rapidly causing further errors on a larger scale. As such, to obtain a perfect forecast, every single error would need to be removed. Forecasting skills have improved over time. Modern forecasts are certainly more reliable than they were before the supercomputer era. The UK’s earliest published forecasts date back to 1861, when Royal Navy officer and meteorologist Robert Fitzroy began to publish forecasts in the Times newspaper. Their methods involved drawing weather charts using observations from a few locations and making predictions based on how the weather evolved in the past when the charts were similar. However, their forecasts were often wrong, and the press were usually quick to criticise. The advent of supercomputers in the 1950s brought so much of insights to the forecasting community. This work paved the way for modern forecasting, the principles of which are still based on the same approach and the same mathematics, although models today are much more complex and predict many more variables. Nowadays, a weather forecast typically consists of multiple runs of a weather model. Operational weather centres usually run a global model with a grid spacing of around 10km, the output of which is passed to a higher-resolution model running over a local area. To reduce the errors, many weather centres also run a number of parallel forecasts, each with slight changes made to the initial snapshot. These small changes grow during the forecast and give forecasters an estimate of the probability of something happening – for example, the percentage chance of it raining. The supercomputer age has been crucial in allowing the science of weather forecasting (and indeed climate prediction) to develop. Modern supercomputers are capable of performing thousands of trillions of calculations per second and can store and process petabytes of data. This means we have the processing power to run our models at high resolutions and include multiple variables in our forecasts. It also means that we can process more input data when generating our initial snapshot, creating a more accurate picture of the atmosphere to start the forecast with. This progress has led to an increase in forecast skill. A neat quantification of this was presented in a Nature study from 2015 by Peter Bauer, Alan Thorpe and Gilbert Brunet, describing the advances in weather prediction as a “quiet revolution”. They show that the accuracy of a five-day forecast nowadays is comparable to that of a three-day forecast about 20 years ago, and that each decade, we gain about a day’s worth of skill. Essentially, today’s three-day forecasts are as precise as the two-day forecast of ten years ago. But is this skill increase likely to continue into the future? This partly depends on what progress we can make with supercomputer technology. Faster supercomputers mean that we can run our models at higher resolution and represent even more atmospheric processes, in theory, leading to further improvement of forecast skill. According to Moore’s Law, our computing power has been doubling every two years since the 1970s. However, this has been slowing down recently, so other approaches may be needed to make future progress, such as increasing the computational efficiency of our models. So, will we ever be able to predict the weather with 100% accuracy? In short, no. There are 2×10⁴⁴ molecules in the atmosphere in random motion – trying to represent them all would be unfathomable. The chaotic nature of weather means that as long as we have to make assumptions about processes in the atmosphere, there is always the potential for a model to develop errors. Progress in weather modelling may improve these statistical representations and allow us to make more realistic assumptions, and faster supercomputers may allow us to to add more detail or resolution to our weather models, but, at the heart of the forecast is a model that will always require some assumptions. However, as long as there is research into improving these assumptions, the future of weather forecasting looks bright. How close we can get to the perfect forecast, however, remains to be seen. This article was originally published on The Conversation by Jon Shonk, Research scientist at the University of Reading. https://theconversation.com/why-the-weather-forecast-will-always-be-a-bit-wrong-101547 To learn more about other climate-related stories occurring across Africa, be sure to click here! © 2018 Oceanographer Daneeja Mawren  Enhanced IR image of four tropical cyclones at 1200UTC 22 Feb 2007 in the South West Indian Ocean. [Source : US Navy/NRL/ (c)EUMETSAT 2007] The Paris Agreement achieved in December 2015 established that the signatory countries should pursue to hold the increase in global average temperature to below 2 °C relative to the preindustrial period and to strive to limit the temperature increase to 1.5 °C below the preindustrial period. A recent study by Muthige et al., 2018 used the Coordinated Regional Downscaling Experiment-Africa regional climate models to downscale six global climate models of the Coupled Model Inter-comparison Project Phase 5 to high resolution. This serves towards studying changes in tropical cyclone tracks over the Southwest Indian Ocean under different extents of global warming (1.5 °C (Fig.3), 2 °C (Fig.4) and 3 °C (Fig.5) of warming with respect to preindustrial conditions). The results projected that the number of tropical cyclones making landfall over southern Africa under global warming will decrease, with 2 °C being a critical threshold, after which the rate of cyclone frequency with further temperature increases no longer has a diminishing effect. Fewer cyclones may bring benefits and reduce damage to the southern African region. Although a decrease in damages associated with flood events is desirable, general decreases in tropical cyclone and tropical lows may also be associated with decreased rainfall over the Limpopo River basin and southern, central and northern Mozambique (with negative impacts on dryland agriculture).
Journal Reference: Muthige, M.S., Malherbe, J., Englebrecht, F.A., Grab, S., Beraki, A., Maisha, T.R. and Van Der Merwe, J., 2018. Projected changes in tropical cyclones over the South West Indian Ocean under different extents of global warming. Environmental Research Letters, 13(6), p.065019. To learn more about other climate-related stories occurring across Africa, be sure to click here! © 2018 Oceanographer Daneeja Mawren  Source : https://earthobservatory.nasa.gov/images/92428/cape-townrsquos-reservoirs-rebound What a difference a few months can make. Cape Town has had to fight tooth and nail to keep itself hydrated and as NASA technology shows us, Theewaterskloof dam has come a long way in such a short space of time. The facility is the largest of its kind in the province and became the “poster child” for the Cape water crisis, as water began to drain from its reserves in 2017. Harsh, prolonged periods of drought meant that Theewaterskloof wasn’t getting replenished, which spelt disaster for the city and its residents. How Theewaterskloof dam fought back from the brink However, the rain finally revisited the Western Cape earlier in 2018. A few cold fronts and heavy rainfall helped stock the dams up with billions of litres of water. Just as important for the Mother City has been the contribution of its water-wise inhabitants. Capetonians have slashed their water consumption rates to record lows, whilst most are adhering to the 50 litres per person, per day rule. In fact, this week is the eight-consecutive period where dam levels have increased. The picture is looking a lot rosier for the region, but more hard work needs to be done to keep the momentum going. Theewaterskloof dam – drought timeline: October 2016 It’s been almost two years since the facility resembled a picture of health. From here onwards, Cape Town’s problems intensified. July 2017 Another dry and humid summer saps the water from the dams. Theewaterskloof is reduced to just 25% of its capacity by the end of the year. January 2018 Dam levels plummet to 16%, large areas of the reservoir are empty and bone dry. March 2018 A barrage of rain in February signals the briefest of relief for the dam. The reserve sees its water levels stabilise, without any great improvement. July 2018 Frequent and persistent rains falling since the middle of May onwards see Theewaterskloof dam soar to 55% of its capacity.
NASA time-lapse for Theewaterskloof dam is available : https://earthobservatory.nasa.gov/images/92428/cape-townrsquos-reservoirs-rebound
To learn more about other high-impact weather and weather-related stories occurring across Africa, be sure to click here! © 2018 Meteorologist Daneeja Mawren |
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