Deriving the slope-mean shielded astronomical solar radiation spectrum and slope-mean possible sunshine duration spectrum over the Loess Plateau

Solar radiation is often shielded by terrain relief, especially in mountainous areas, before reaching the surface of the Earth. The objective of this paper is to study the spatial structures of the shielded astronomical solar radiation(SASR) and the possible sunshine duration(PSD) over the Loess Plateau. To this end, we chose six test areas representing different landforms over the Loess Plateau and the software package of Matlab was used as the main computing platform. In each test area, 5-m-resolution digital elevation model established from 1:10,000 scale topographic maps was used to compute the corresponding slope, SASR and PSD. Then, we defined the concepts of the slope-mean SASR spectrum and the slope-mean PSD spectrum, and proposed a method to extract them from the computed slope, SASR and PSD over rectangular analysis windows. Using this method, we found both spectrums in a year or in a season for each of the four seasons in the six test areas. Each spectrum was found only when the area of the corresponding rectangular analysis window was greater than the corresponding stable area of the spectrum. The values of the two spectrums decreased when the slope increased.Furthermore, the values of the stable areas of the spectrums in a year or in a season were positively correlated with the variable coefficients of the slope or the profile curvature. The values of the stable areas of the two spectrums in a year or in a season may represent the minimum value of test areas for corresponding future research on the spatial structures of the SASR or PSD. All the findings herein suggest that the spatial structures of the PSD and the SASR are caused by the interactions between solar radiation and terrain relief and that the method for extracting either spectrum is effective for detecting their spatial structures. This study may deepen our understanding of the spatial structure of solar radiation and help us further explore the distribution of solar energy in mountainous regions.

Trends in sunshine duration and atmospheric visibility in the Yunnan-Guizhou Plateau,1961-2005

Using the observed data from 184 stations over the Yunnan-Guizhou Plateau （YGP） from 1961 to 2005, the long-term trends in sunshine duration, cloud amount, dry visibility （Vd）, dry extinction, and water vapor over the YGP are analyzed. The results show that 85% of the stations recorded shortening annual sunshine duration, with the decrease rates between -12.2 and -173.7 h/10yr. Results of Mann-Kendall tests indicate that, among the stations with decreasing sunshine duration, 63.7% of them experienced an abrupt change that started in the 1970s and peaked in the 1980s. This decreasing trend has reversed in the early years of the 21st century. The cloud cover and water vapor content in the mid and lower levels over the YGP had no obvious changes during the study period. The annual averages of Vd declined from 34 km in the 1960s to 27 km at present. The annual mean dry extinction coefficient trended upward, from 0.176 to 0.190, on the YGP from 1980 to 2005. Analyses of cloud cover, water vapor, atmospheric visibility, and dry extinction coefficient revealed that emitted tropospheric aerosols （including air pollutants） resulting from increased energy consumption over the YGP could be a major Factor influencing the reductions of sunshine duration and atmospheric visibility.

Spatial-temporal Variation Characteristics of Sunshine Duration in China and Its Influence Factors

Sunshine duration has an important impact on agriculture.In order to study the temporal and spatial variation of sunshine duration in China under the background of climate change,based on the observation data of 2089 national meteorological stations during 1961-2017,trend analysis,mutation analysis,partial correlation analysis,and Mann-Kendall mutation analysis were used to analyze the temporal and spatial variation characteristics of sunshine duration in different regions of China,and the influence of main climatic factors and human activities.The results showed that:the sunshine duration in China showed a significant decreasing trend with a rate of-45.8 h/10 a,and the sunshine duration in 7 regions of Northwestern China,Northern China,Northeastern China,Center China,Eastern China,Southern China,and Southwestern China also showed a significant decrease.The spatial distribution of sunshine duration in China was characterized by"less in the south and more in the north",and the sunshine duration in the northern region was significantly higher than those in the southern region.The sunshine duration in Tibet,Qinghai,Gansu and west Inner Mongolia was higher,while it was obviously lower in Sichuan Basin.Through M-K mutation test analysis,it was found that sunshine duration in the whole country decreased significantly,but there was no mutation station,while mutation occurred at 1989 in Southwestern China,1983 in Northwestern China,1985 in Northeastern China.Seasonally,there was the highest sunshine duration in summer,followed by spring,autumn,and winter;the decline rate was also the highest in summer,followed by autumn,winter,and spring.Sunshine duration had a highly negative correlation with total cloud amount,visibility,haze,and precipitation,while had a strongly positive correlation with wind speed,and had no significant correlation with fog.

Error Analysis and Correction of Sunshine Duration Sensor

Beginning with the analysis on the principle of photoelectric sunshine duration sensor and combining with the problems occurred in use,various factors affecting the accuracy of observation are discussed. The digital sunshine duration sensor solutions are put forward by analysis on the data detection and observation,the corrections on the error factors are discussed,such as directional response characteristic,stray light and temperature characteristic. As a consequence,the precision of the sunshine duration with automatic observation is improved.

Spatiotemporal changes in sunshine duration and its influential factors in Chongqing,China from 1961 to 2020

The surface solar radiation in most parts of the world has undergone a phenomenon known as global dimming and brightening,characterized by an initial decrease followed by an increase.As a result,the sunshine duration(SD)has decreased in the past 60 years.Against the backdrop of global dimming and brightening,SD has decreased to varying degrees in many regions of China.Using the observed data of SD,cloud amount(total cloud amount and low cloud amount,abbreviated as TCA and LCA),precipitation,and relative humidity(RH)from 34 meteorological stations in Chongqing during the period of 1961-2020,along with a digital elevation model(DEM)with a resolution of 90 m,this study analyzed the spatiotemporal variations and influencing factors of SD.The analysis employed methods such as linear regression,Mann-Kendall test,wavelet transformation,and DEM-based possible SD distributed model.The results showed that the annual SD in Chongqing has significantly decreased over the last 60 years,with a decreasing interannual trend rate(ITR)of 40.4 h/10a.Except for no obvious trend in spring,SD decreased significantly in summer,autumn and winter at the ITR of 21.1 h/10a,8.5 h/10a and 7.5 h/10a,respectively.An abrupt decrease in the annual SD was found in 1979.The difference before and after the abrupt decrease was 177.7 h.The difference before and after the abrupt decrease was 177.7 h.The annual SD possessed the oscillation period of 11a.The spatial heterogeneity of the mean annual SD during the last 60 years was obvious.The distribution of SD in Chongqing is high in the northeast and low in the southeast.In addition,about 73%of the total area in Chongqing showed a significant and very significant decreasing trend.The regions with significant changes are mainly concentrated in the regions with altitudes of 200~1000 m.The increasing LCA was the main cause of the decrease of the annual SD in the regions with 200-400 m altitude decreased the most and changed the most.Increasing LCA is the primary cause of the reduction in annual SD,showing a strong negative correlation coefficient of-0.7292.In Chongqing,PM2.5 concentration showed a significant decrease trend in annual,spring,autumn and winter during 2000-2020,but the significant correlation between PM2.5 concentration and SD was only in autumn and reached an extremely significant level.

Variation in Sunshine Duration and Related Aerosol Influences at Shangdianzi GAW Station, China: 1958–2021

Sunshine duration(SD) is adopted widely to study global dimming/brightening. However, long-term simultaneous measurements of SD and closely related impact factors require further analysis to elucidate how and why SD has varied during the past decades. In this study, a long-term(1958–2021) SD data series obtained from the Shangdianzi Global Atmosphere Watch(GAW) station in China was analyzed to detect linear trends, climatic jumps, and climatic periods in SD using linear fitting, the Mann–Kendall trend test, and the continuous wavelet transform method. Annual SD exhibited steady dimming(-67.3 h decade-1) before 2010, followed by a period of brightening(189.9 h decade-1)during 2011–2020. An abrupt jump in annual SD occurred in 1995, and the annual SD anomaly exhibited significant oscillation with ~3-yr periodicity during 1960–1978. Partial least squares analysis revealed that annual SD anomaly was associated with variations in relative humidity, gale days, cloud cover, and black carbon(BC). Further analysis of the clear-sky daily sunshine percentage(DSP) and simultaneous measurements of aerosol properties, including aerosol optical depth, aerosol extinction coefficient, single scattering albedo(SSA), BC, and total suspended particulates, suggested that variation in DSP was affected primarily by aerosol scattering and absorption. Furthermore, the hourly clear-sky SD at high aerosol loading was approximately 60% and 56% of that at middle and low aerosol loadings, respectively. The pattern of diurnal variation in clear-sky hourly SD, as well as the actual values, can be affected by the fine particulate concentration, aerosol extinction coefficient, and SSA.

Estimation of Daily Global Solar Radiation with Different Sunshine-Based Models for Some Burundian Stations

Sunshine duration (S) based empirical equations have been employed in this study to estimate the daily global solar radiation on a horizontal surface (G) for six meteorological stations in Burundi. Those equations include the Ångström-Prescott linear model and four amongst its derivatives, i.e. logarithmic, exponential, power and quadratic functions. Monthly mean values of daily global solar radiation and sunshine duration data for a period of 20 to 23 years, from the Geographical Institute of Burundi (IGEBU), have been used. For any of the six stations, ten single or double linear regressions have been developed from the above-said five functions, to relate in terms of monthly mean values, the daily clearness index () to each of the next two kinds of relative sunshine duration (RSD): and . In those ratios, G0, S0 and stand for the extraterrestrial daily solar radiation on a horizontal surface, the day length and the modified day length taking into account the natural site’s horizon, respectively. According to the calculated mean values of the clearness index and the RSD, each station experiences a high number of fairly clear (or partially cloudy) days. Estimated values of the dependent variable (y) in each developed linear regression, have been compared to measured values in terms of the coefficients of correlation (R) and of determination (R2), the mean bias error (MBE), the root mean square error (RMSE) and the t-statistics. Mean values of these statistical indicators have been used to rank, according to decreasing performance level, firstly the ten developed equations per station on account of the overall six stations, secondly the six stations on account of the overall ten equations. Nevertheless, the obtained values of those indicators lay in the next ranges for all the developed sixty equations:;;;, with . These results lead to assert that any of the sixty developed linear regressions (and thus equations in terms of and ), fits very adequately measured data, and should be used to estimate monthly average daily global solar radiation with sunshine duration for the relevant station. It is also found that using as RSD, is slightly more advantageous than using for estimating the monthly average daily clearness index, . Moreover, values of statistical indicators of this study match adequately data from other works on the same kinds of empirical equations.

A Remote Sensing Model to Estimate Sunshine Duration in the Ningxia Hui Autonomous Region,China

Sunshine duration（SD） is strongly correlated with solar radiation, and is most widely used to estimate the latter. This study builds a remote sensing model on a 100 m × 100 m spatial resolution to estimate SD for the Ningxia Hui Autonomous Region, China. Digital elevation model（DEM） data are employed to reflect topography, and moderate-resolution imaging spectroradiometer（MODIS） cloud products（Aqua MYD06-L2 and Terra MOD06-L2） are used to estimate sunshine percentage. Based on the terrain（e.g.,slope, aspect, and terrain shadowing degree） and the atmospheric conditions（e.g., air molecules, aerosols,moisture, cloud cover, and cloud types）, observation data from weather stations are also incorporated into the model. Verification results indicate that the model simulations match reasonably with the observations,with the average relative error of the total daily SD being 2.21%. Further data analysis reveals that the variation of the estimated SD is consistent with that of the maximum possible SD; its spatial variation is so substantial that the estimated SD differs significantly between the south-facing and north-facing slopes,and its seasonal variation is also large throughout the year.

Trends of the sunshine duration and diffuse radiation percentage on sunny days in urban agglomerations of China during 1960–2005

The long-term observational data of sunshine duration（SD） and diffuse radiation percentage（defined as diffuse solar radiation/total solar radiation, DRP） on sunny days during 1960–2005 were analyzed in 7 urban agglomerations and the whole of China. The results show that the sunny sunshine duration（SSD） has decreased significantly except at a few stations over northwestern China in the past 46 years. An obvious decrease of the SSD is found in eastern China, with the trend coefficients lower than-0.8. Accompanied by the SSD decline, the sunny diffuse radiation percentage（SDRP） in most stations shows obvious increasing trends during the 46 years. The averaged SDRP over China has increased 2.33%per decade, while the averaged SSD shows a decrease of-0.13 hr/day per decade. The correlation coefficient between SDRP and SSD is-0.88. SSD decreased over urban agglomerations（small to large city clusters） in the past 46 years, especially in large cities and medium cities, due to the strong anthropogenic activities and air pollution represented by aerosol option depth（AOD） and tropospheric column NO2（Tro NO2）. On the regional scale, SSD has an opposite trend from SDRP during 1960 to 2005, and the variation trends of regional mean values of SSD and SDRP in southeastern China are more pronounced than those in northwestern China.

Comparison of Sunshine Duration Measurements between a Jordan Sunshine Recorder and Three Automatic Sensors at Shangdianzi GAW Station

We used parallel sunshine duration datasets obtained with a Jordan sunshine recorder and three automatic sunshine duration sensors to investigate the differences between these instruments.We used measurements obtained at Shangdianzi(SDZ)regional Global Atmosphere Watch(GAW)station with a Jordan sunshine recorder,a DFC2 photoelectric sunshine meter,a CHP1 pyrheliometer,and two CMP11 pyranometers from 1 January to 5 July 2019 and from 3 November 2020 to 28 February 2021.The results showed that the daily sunshine duration measurements obtained from the Jordan sunshine recorder were comparable with those from the DFC2 meter and the CMP11 pyranometers under all-sky conditions,but were considerably different from those observed by the CHP1 pyrheliometer.An analysis of potential influencing factors showed that the solar zenith angle,the spectral range of the automatic sensors,the relative humidity,and the sky conditions were the main factors affecting the measurements of sunshine duration between the Jordan sunshine recorder and three automatic sensors.We proposed a simple linear regression function-the DFC2-equivalent sunshine duration estimation(DFCESD)model—to guarantee the consistency of the long-term sunshine duration series observed by the Jordan sunshine recorder at SDZ and the measurements from the DFC2 meter.Validation of the DFCESD model showed that the mean absolute difference(MAD)between the daily sunshine duration observed by the Jordan sunshine recorder and those from the DFC2 meter improved from-0.7 to-0.2 h day^(-1),the relative deviation(RD)improved from-9.3%to-2.3%,and the root-mean-square deviation(RMSD)decreased from 1.0 to 0.8 h day^(-1).

Study on the Characteristics of Sunshine Hours Changes in Tacheng Basin in Recent 50 Years

[Objective] The aim was to study the characteristics of sunshine hour changes in Tacheng in recent 50 years.[Method] By dint of the measured data of annual,seasonal and monthly sunshine hour’s changes in four meteorological observatories from 1960 to 2009,using linear regression analysis method,the characteristics of sunshine hour changes in Tacheng in recent 50 years were studied.[Result] The results showed that the annual average sunshine hours in Tacheng Basin in recent 50 years were above 2 800.0 h,among which Tacheng,Yumin had the most,2 936.1,2 921.3 h respectively and Emin the least,2 814.2 h.The sunshine hours were the most in autumn and summer,followed by winter,and were least in spring;sunshine hours during growth season in Tacheng and Yumin were the most,followed by Emin and then Tuoli.The linear tendency rate of sunshine hours in four stations in February was negative.But only the value in Tacheng,Emin decreased at a rate of-4.7 and-6.0 respectively;the linear tendency rate of sunshine hours in four stations in May,June and October were positive,but only Yumin station mounted at a rate of 14.5,12.6,11.2 h/10 a.The linear tendency of seasonal sunshine hours during the year and the growth season increased in Yumin at a rate of 74.9 and 60.5 h/10 a.The linear tendency rate of sunshine hours in four stations in winter was negative,among which the rate of Tacheng,Emin and Tuoli decreased at a rate of-5.5,-6.7,-4.9 h/10 a;that in other three seasons,only in Yumin,it increased most rapidly at a rate of 9.7,7.7 and 7.0 h/10 a.[Conclusion] The study provides theoretical reference for the adjustment and perfection of husbandry industry structure and optimization,reasonable development and utilization of solar energy resources.

近60年大连市日照变化规律及气象条件影响(英文)

[Objective] The change law and meteorological factor of sunshine duration in Dalian in recent 60 years were studied.[Method] Based on the statistical data of sunshine duration from base station in Dalian City from 1951 to 2009,the annual,seasonal,and monthly variation of sunshine duration in recent 60 years were analyzed,as well as its relationship with meteorological factors,and sunshine duration was detected by means of climate mutation theory.[Result] Annual sunshine duration in Dalian in recent 60 years showed decrease trend on the whole,and its climatic variation rate was-3.31 h/a,with larger annual variation,namely the difference between maximum value(1978) and minimum value(2003) reached 681 h;there was obvious seasonal variation in sunshine duration,with the order of autumn>summer>winter>spring,and their climatic variation rate were-1.18,-1.15,-0.91 and-0.62 h/a;except for March,sunshine duration in each month went down,especially October,while there was slight increase in March;sunshine percentage had inverse correlation relationship with total cloudiness,relative humidity and heavy fog days;annual sunshine duration reduced abruptly around 1983.[Conclusion] Our study could provide scientific foundation for the development of agriculture and forestry in Dalian City.

Trends in the Different Grades of Precipitation over South China during 1960–2010 and the Possible Link with Anthropogenic Aerosols

Using observed daily precipitation data to classify five levels of rainy days by strength in South China （SC）,with an emphasis on the Pearl River Delta （PRD） region,the spatiotemporal variation of different grades of precipitation during the period 1960-2010 was analyzed and the possible link with anthropogenic aerosols examined.Statistical analysis showed that drizzle and small precipitation has significantly decreased,whereas medium to heavy precipitation has increased slightly over the past 50 years （although not statistically significant）.Further data analysis suggested that the decline in drizzle and small precipitation probably has a strong link to increased concentrations of anthropogenic aerosols produced by large-scale human activities related to the rapid socioeconomic development of the PRD region.These aerosols may also have led to the obvious decreasing trend in horizontal visibility and sunshine duration in SC,which is statistically significant according to the t-test.

Observation seasonal variation of intraocular pressure in young healthy volunteers

AIM:To investigate fluctuation of intraocular pressure(IOP)and seasonal variation of 24-hour IOP during one year in healthy participantsMETHODS:Totally 13 young healthy volunteers participated in this study.IOP was measured with Canon TX-20 at about 8:00-9:00 a.m.from Monday to Friday every week for a whole year.They also underwent 24-hour IOP examination every three months.Blood pressure,heart rate,temperature,humidity,atmosphere pressure,sunshine duration and other environment parameters were recorded.RESULTS:The yearly fluctuation curve showed IOP in the summer months were lower than other seasons.In the multivariable generalized estimating equation analysis,IOP had a negative correlation with both temperature and sunshine duration(P<0.05).There also was a seasonal effect on 24-hour IOP.However,all intraclass correlation coefficients values of minimum,maximum and average of the 24-hour IOP and each individual IOP were less than 0.30.CONCLUSION:IOP is trend to be higher in cold days than warm days.IOP have negative association with both environmental temperature and duration of sunshine.On a season-to-season basis,24-hour IOP is not highly reproducible in healthy volunteers.

Study on Climate Change Characteristics in Western Qinling in the Past 41 Years

[Objective] The research aimed to examine climate change characteristics in western Qinling during 1967-2007. [Me^od] Based on the data of temperature, precipitation, sunshine duration, relative humidity and evaporation capacity derived from 17 weather stations, we analyzed the climatic change characteristics in western Qinling in the past 41 years, r Result] Increase magnitude of the annual mean temperature was 0.30 ℃/10 a in the past 41 years. Annual precipitation averaged 802 mm and varied non-significantly during the 41 years, while precipitation in spring significantly decreased by 13.68 mm/10 a. Besides, annual sunshine duration and annual mean relative humidity both decreased non-significantly, in contrast to annual evaporation capacity which showed an insignificantly increasing trend. Compared among southern, central and northern areas of the western Qinling, annual mean temperature, precipitation and relative humidity showed decreasing trends from south to north, while annual sunshine duration and annual evaporation capacity showed inversely increasing trends. [ Condusionl Thus, our research could provide reference basis for ecosystem stability and related research in western Qinling.

Temporal variations of reference evapotranspiration and controlling factors:Implications for climatic drought in karst areas

Variations in reference evapotranspiration(ET_(0)) and drought characteristics play a key role in the effect of climate change on water cycle and associated ecohydrological patterns.The accurate estimation of ET_(0) is still a challenge due to the lack of meteorological data and the heterogeneity of hydrological system.Although there is an increasing trend in extreme drought events with global climate change,the relationship between ET_(0) and aridity index in karst areas has been poorly studied.In this study,we used the Penman-Monteith method based on a long time series of meteorological data from 1951 to 2015 to calculate ET_(0)in a typical karst area,Guilin,Southwest China.The temporal variations in climate variables,ET_(0)and aridity index(AI)were analyzed with the Mann-Kendall trend test and linear regression to determine the climatic characteristics,associated controlling factors of ET_(0) variations,and further to estimate the relationship between ET_(0) and AI.We found that the mean,maximum and minimum temperatures had increased significantly during the 65-year study period,while sunshine duration,wind speed and relative humidity exhibited significant decreasing trends.The annual ET_(0) showed a significant decreasing trend at the rate of−8.02 mm/10a.However,significant increase in air temperature should have contributed to the enhancement of ET_(0),indicating an“evaporation paradox”.In comparison,AI showed a slightly declining trend of−0.0005/a during 1951-2015.The change in sunshine duration was the major factor causing the decrease in ET_(0),followed by wind speed.AI had a higher correlation with precipitation amount,indicating that the variations of AI was more dependent on precipitation,but not substantially dependent on the ET_(0).Although AI was not directly related to ET_(0),ET_(0)had a major contribution to seasonal AI changes.The seasonal variations of ET_(0)played a critical role in dryness/wetness changes to regulate water and energy supply,which can lead to seasonal droughts or water shortages in karst areas.Overall,these findings provide an important reference for the management of agricultural production and water resources,and have an important implication for drought in karst regions of China.

Effects of Light on Tree Growth

Empirical equations were used to fit tree growth through the analysis of parse wood data, functions with tree growth amount as the dependent variable and annual sunshine duration as the independent variable. According to arithmetical operations like derivation of the functions, the relative contribution rate of light to tree growth was 64.8%, which was almost equal to the relative contribution rate of precipitation to tree growth. Therefore, the light and precipitation were of equal importance to tree growth.

Modeling of Climatic Parameters and Determination of Climatic Differences in the City of Elazig-Turkey and its Close Regions

This study deals with the climatic parameters and the climatic differences in Elazig and its close regions (cities of Malatya, Tunceli, Bing?l, Erzincan). Data on mean monthly temperature, daily maximum-minimum temperature, rela-tive humidity, pressure, wind speed, rainfall, solar radiation and sunshine duration were analyzed and modeled for 10-year period, from 1994 to 2003. Malatya city was the hottest area whole period, while the Erzincan city was the coldest area. Maximum temperatures were at highest values in Tunceli. Minimum temperatures reached the warmest values in the Malatya. Erzincan city was the most humid area almost throughout the period while Malatya was the least humid area. Wind speed reached the highest values in the Elazig and the lowest values in the Tunceli. Pressure reached the highest values in the Malatya and the lowest values in the Erzincan. Direct solar radiation reached the highest val-ues in the Tunceli and the lowest values in the Erzincan. Sunshine duration reached the highest values in the Malatya and the lowest values in the Erzincan. A regression analysis was carried out by using the linear regression technique to model the climatic parameters. The models developed can be used in any study related to climatic and its effect on the environment and energy. The models developed in this study can be used for future predictions of the climatic parame-ters and analysing the environmental and energy related issues in Elazig and its close regions (cities of Malatya, Tun-celi, Bing?l, Erzincan).

Climatic variables: Evaporation, sunshine, relative humidity, soil and air temperature and its adverse effects on cotton production

Cotton yield is a function of growth rates,flower production rates,and flower and boll retention during the fruiting period.Information on the relationship between climatic factors and the cotton plant’s ability to produce and sustain flower buds,flowers,and bolls will allow one to model plant responses to conditions that frequently occur in the field and to predict developmental rate or the formation of these organs.This study investigates the statistical relationship between various climatic factors and overall flower and boll production.Also,the relationship between climatic factors and production of flowers and bolls obtained during the development periods of the flowering and boll stage.Further,predicting effects of climatic factors during different convenient intervals(in days)on cotton flower and boll production compared with daily observations.Evaporation,sunshine duration,relative humidity,surface soil temperature at 1800 h,and maximum air temperature,are the important climatic factors that significantly affect flower and boll production.The five-day interval was found to be more adequately and sensibly related to yield parameters.Evaporation;minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention.There was a negative correlation between flower and boll production and either evaporation or sunshine duration,while that correlation with minimum relative humidity was positive.