Climate Change Impact - Part 9 - Kyrgyzstan

Climate Change Impact


Part 9: Example –Kyrgyzstan


Summary

Kyrgyzstan has a continental climate with cold winters and hot summers. Most of the rain falls in the summer months and temperatures are below freezing for most of the winter months. It is projected that storm rainfall will increase by up to 20% and that the duration of lying snow will decrease.

Introduction

Kyrgyzstan is in central Asia and has severe winters with temperature below zero for many months, particularly in mountainous areas.



Figure 1 Map of Kyrgyzstan showing project road

Climate change can affect roads in many ways. The most obvious is storm rainfall; an increase in storm rainfall could require modification to current design for culverts and longitudinal drains. Other factors include daily temperature range, which could affect expansion joints, and maximum temperature, which could affect the choice of binding agent.

Once current values of these parameters have been determined then the extent to which they will change in the future can be assessed.

The observed climate data were downloaded from internet sites which process data facilitated by international organisations such as the World Meteorological Organisation.

Other documents related to climate change for Kyrgyzstan were downloaded. These included:

  •         UNFCCC Country Brief 2014: Kyrgyzstan
  •         Climate Profile of the Kyrgyz Republic
  •         The Kyrgyz Republic: Intended Nationally Determined Contribution
  •         The Kyrgyz Republic’s Second National Communication to the United Nations Framework Convention on Climate Change

These documents describe the potential change to the climate in general terms but were not specific enough for road design.

Current Climate

Kyrgyzstan has a continental climate with warm summer and cold winters.

 The following chart shows the location of the climate stations which were used to determine current climate parameters. Only stations in the area of the project road are shown. The data were at a daily time step and included: precipitation, depth of snow, average daily temperature, daily maximum temperature and daily minimum temperature. Data were downloaded for the period 1950 to the present.

Figure 2 - Location of sites with climate data


Figure 2 shows the location of sites with climate data. Sites with a solid diamond have precipitation, temperature and snow data. Sites with an open diamond only have precipitation data.

The chart also shows the area covered by the nearest climate model cell as an orange rectangle. It is convenient that the section of road of interest corresponds to one of the climate cells.

Rainfall is highest in the summer months. In winter, average monthly temperatures are often below zero. The road itself passes between two areas with higher elevations and maximum daily rainfall is lower than areas with higher land – around 20 mm per day.

Climate projections

To examine the performance of climate models, their simulation relative to past observed climate for the period 1970 to 1990 was examined. The four models chosen on this basis were:

  •         bcc-csm1-1: Beijing Climate Center Climate System Model (China)
  •         IPSL-CM5A-MR: The Institut Pierre Simon Laplace (France)
  •         CCSM4: The Community Climate System Model Version 4 (USA)
  •         NorESM1-M: Norwegian Earth System Model (Norway)


The conclusions relating to climate change and daily maximum rainfall were:

  •   The average percentage increase for the final 50 years of the present century is 7.3% for the RCP 8.5 projections and 5.5% for the RCP 6.0 projections.
  • The projections of 5-day rainfall, more relevant for rivers which are crossed by the road showed a similar increase which could be translated in into increased flooding.
  • Winter and summer temperatures have been rising in recent years. The rate of increase has been 3.3 °C per century, slightly lower than the projected 5.5 °C per century. This significance of these increases relate to icing in winter and the heat-resistance of the road surface in summer. There is no indication that the diurnal temperature range (important for expansion joints) will increase.
  • On average, the depth of snow reaches 500 mm or even more in an average year.
·         When a range of models was ranked on the projected increase between the present and the year 2100, the difference in projection between the upper and lower quartile was quite modest; of the order of 15%. This applied for both RCP 6.0 and RCP 8.5.

·         When four selected models were compared their difference in projected values for the year 2100 was larger.

·         In most cases the largest percentage increase in daily rainfall for any projection occurred not in the final year of this century but in an earlier year. At any time in the current century the increase in precipitation rarely exceeded 20%, apart from the few models with the highest rate of increase in precipitation. A further consideration following from this is that the maximum increase in rainfall could occur during the projected life of the road.


There are no specific projections related to snow depth. Figure 3 shows two alternative metrics. The first is ‘icing days’; these are days when the daily maximum temperature is below zero. The second is ‘frost days’; these are days when the daily minimum temperature is below zero. The decline in these two variables indicates two things. Firstly, that snow fall will be less frequent and secondly that it will lie for a shorter time.


Figure 3 Days with temperature below freezing for all or part of a day

Conclusions

The main conclusions are that there will be an increase in storm rainfall of up to 20% during the life of the road. The period with lying snow will reduce.








Comments

SEA ICE AND SNOW

The Georgia Institute of Technology has recently released details of a study of the relationship between Arctic Sea Ice and Northern Hemisphere Snow Cover. The press release summarises it as “The researchers analyzed observational data collected between 1979 and 2010 and found that a decrease in autumn Arctic sea ice of 1 million square kilometers -- the size of the surface area of Egypt -- corresponded to significantly above-normal winter snow cover in large parts of the northern United States, northwestern and central Europe, and northern and central China.”

This goes some way to explaining the fact that whereas Arctic Sea Ice has been tending to decrease (at 53,000 km2/year) snow coverage has declined more slowly (at 22,000 km2/year). The importance of snow and ice is their role in the albedo feed-back mechanism. Snow reflects almost all the incoming energy, water and land (at least the northern boreal forests where most snow falls) reflect about 10%. So, other things being equal, the influence of snow and ice are equivalent. But, and it’s a big but, other things are not equal. Both sea ice and snow cover vary seasonally. The following chart shows average monthly values for the period 1978 to 2011. This shows that in winter snow covers a much larger area than sea ice.





However the albedo effect is only applicable when the sun is above the horizon. The next chart shows the areas adjusted for solar angle. In this case we have assumed a latitude of 80 °N for sea ice and 70 °N for snow and multiplied areas in the first chart by the sine of the sun angle at midday on the 15th of each month. (Calculated using the tool at http://aa.usno.navy.mil/data/docs/AltAz.php). This presents a very different picture and suggests that the influence of snow and ice are equivalent – with snow being perhaps more predominant.





This calculation is subject to a large number of caveats. The sea ice area is based on NSIDC ‘sea ice extent’ which shows “the total area of ocean covered with at least 15 percent ice”. This is reasonable as a metric since sea ice is almost 90% below water but of course such ice is not reflecting radiation. The use of 70 °N and 80 °N respectively and mid-day sun angle are also only approximate. Ideally it would be necessary to track areas of ice and snow at different times of the year, at different latitudes and the energy reflected at different times of day. 

The final chart shows the solar-angle adjusted ice and snow area. This was calculated as for the previous chart. It shows that despite the snow area being larger and reducing less than the albedo adjusted ice area has shown a steady decline.


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