چكيده لاتين :
Introduction
Climate change r~fers to changes in weather behavior of a region to behave during a
long-term time horizon of the recorded data in area that is expected. Greenhouse
gases increasing in future periods, thus exacerbating climate parameters change, can
be have many negative effects on different systems including water resources,
environment, industry, health, agriculture and all the systems that are interaction
with the climate. The negative consequences of this phenomenon can be destructive
to mankind so much that among tens threatening factors of Human in the 21st
century (poverty, nuclear weapons, food shortage, etc.) the climate change accounted for first place. IPCC report indicates that if the Current trends of fossil fuels
consume be continue, the concentration of greenhouse gases before the end of the
21st century could be reached to more than 600 p.p.m. Resulting average of increase
in the surface temperature of the planet by 2100 could reach 1.1 to 6.4°C and causes
of climate change.
In recent years, different Extreme events including floods and droughts have
happened in Babul-rod watershed which emphasizes necessity to investigate further
on impact of climate change on watershed hydrology. It should be noted that usually
in hydrological studies, models computational cells of the atmosphere-ocean general
circulation climate is greater than study area. So in these studies is needed to
downscaling output models. Due to large scale of computational grid for GCMs, they
are not able to predict meteorological factors for point scale. Hence it is necessary to
use Weather Generator (WG) tool to predict meteorological factors in point scale
which weather generator with the help of numerical models output, can be evaluated
climate change on a point scale and the desired station. Choice of used models and
scenarios by the Intergovernmental climate.change standards, the availability and use
them in previous studies was conducted.
Materials and Methods
In this study, using this method, data HadCM3 general circulation models using LARSWG
model under two scenarios A2 and Bl for long periods 2065-2046 and 2099-2080
were downscaled. HadCM3 consists of two components Oceanic and Atmospheric
models. High resolution of the oceanic component is the main advantage of this
model. Among other advantages of this model is the good coordination between the
Oceanic and Atmospheric components. Characteristics of used emission scenarios in
this study (A2 and Bl) include: (a) scenarios A2 (pessimistic): scenario of a world
where countries act independent and are self-reliant. The world's population increases and economic development is regional. (b) Scenario B1 (optimistic}:
According to this scenario, the integration and convergence with population growth
in the last half century (2050} and then the gradual decline of the same opinion the
A2 scenario is mentioned. In scenario B1, witnessed a rapid change of economic
structure and economic information services as well as introducing clean technology
and emissions reduction will be effective. The study area Babolrood watershed is one
of the ten watershed great Mazandaran province in northern Iran, with an area of
over 51,725 hectares, between 52° 38' to 52° 55' eastern longitude and 36 o 2 'to 36°
22' northern latitude. In this study is used required data model, long-term statistics
available weather stations Babolsar (63 years} and Gharakheil (43 years} for the
radiation and sunshine duration and climatological and hydrometric stations
Gloogah-Bandpei (40 years} located in the center of the basin, to the amount of
rainfall, minimum temperature, maximum temperature has hit a 30-year base period
1982-2011 was perfect. After data and information collecting for the study area, do
the homogeneity test and data modifying. Next, the ability of LARS-WG model in
climate modeling study period of base stations, based on the base case scenario was
investigated. For evaluation model outputs, were compared the observed and
simulated data included of four variable minimum temperature, maximum
temperature, precipitation and radiation using Student's T- test, statistical
coefficients Nash - Sutcliffe, RMSE and R2 with each other.
Discussion and Conclusion
Statistical analysis of modeling results between observed and simulated data;
maximum and minimum temperatures and sunshine hours good match and just in
precipitation case there is very little difference. Overall results show the ability of
LARS-WG model in modeling climate Babolrood watershed is based on the base case
scenario. In the next step Model Outputs under A2 and B1 climate scenarios for the periods 2046-2065 and 2080-2099 were obtained on a global scale and the scale
became station. Finally, using the results obtained, Babolrood watershed climate
change under the climate scenarios was evaluated.
Considering the results predicted changes in precipitation for the A2 scenario was
determined, first period falls in most years except rainy months {March, April,
October and November}. The second period in more months except April, October
and November was much reduced. The results of the scenario Bl, represents the
predicted reduction in rainfall in all months except ones rainy {April, October and
November) is the highest rate of decline in the first and second periods, respectively,
23 and 34 mm for the month of August. These results indicate Babolrood of reviews
elderly basin, average annual rainfall has decreased by about 37.5 mm and 85.8 mm
in the first period and the second period respectively. The results revealed that
change in rainfall in Babul-rod watershed varies between -43% to +32%, which is
accompanied with rainfall increase in rainy months and severe decrease in months
with low rain, respectively.
The results of predicting changes in minimum temperature for the A2 scenario show
that the minimum temperature was elevated in all year's months. The highest
increase in the minimum temperature for the month of July in the first and second
periods respectively 2.4 and 4.7 degrees Celsius and January is the lowest rate of
increase in the minimum temperature in the first and second periods respectively the
amount of 1.2 and 2.5 •c. Considering the scenario Bl, the highest and lowest
minimum temperature to increase, respectively, July in the first period {1.8 ·q and
second {2.8 ·q and January in the first period {0.8 ·q and November in the second
period {1.5 ·q will be.
The results of the predicted maximum temperature changes A2 scenario shows an
increase in the maximum temperature in all year's months are compared to the
baseline forecast. The highest maximum temperature rise for the month is July in the first period {2.6 oq and August in the second period {5.1 °C). The lowest increase in
the maximum temperature of the first period was January {1 oq and the second in
February {2.3 °(}. The results of the scenario B1 suggests that the greatest increase in
the maximum temperature on July in the first period {2 o C) and August in the second
period {3.2 oq respectively. February also in the first period {0.6 oq and November in
the second period {1.6 oc} temperature rise will be minimal. It also gives the results
suggest that the average maximum temperature Babolrood watershed in the future
average 1.3 oc {optimistic and the first period} to 3.5 oc {pessimistic and the second
period} will increase Correspond.
Conclusion
Precipitation in the basin 2046-2065 and 2080-2099 periods Babolrood will vary from
-43 to +32 percent, accounting changes with an increase in rainfall in the rainy
months {March, April, October and November} and intensive low rainfall in summery
months. The average annual rainfall has decreased by about 37.5 mm and 85.8 mm in
the first period and the second period respectively. Also, Increase in annual
temperature in average was 1.5c -2.8c, especially in warm months which cause low
snow- falling. Increase in rainfall amount . for cold months, and increase in
temperature for warm months, through affecting regional climate in the Babul-rod
watershed, will cause change in extreme events frequency. Accordingly, and with
regard to changes in precipitation, river basin Babolrood will go to the drier latest.
The regional climate in the near future, likely frequency and intensity of extreme
floods and droughts will increase greatly. In fact, in recent years witnessed the
disaster areas in the northern provinces Babolrood and we need to investigate
further the effects of climate change on the hydrological basin and emphasize the
degree components.
