Uran Chung

Urban-Effect Correction to Improve Accuracy of Spatially Interpolated Temperature Estimates in Korea

Abstract Gridded temperature data are frequently used to run ecological models at regional scales and are routinely generated by spatially interpolating point observations at synoptic weather stations. If synoptic stations are located in urbanized areas, observed temperature and the interpolated data could be contaminated by the urban heat island effect. Without an appropriate correction, temperature estimates over rural areas or forests might deviate significantly from the actual values. This study was conducted to remove the urban effects embedded in the interpolated surfaces of daily minimum temperature in South Korea, where most weather stations are located in urbanized or industrialized areas. To overcome the spatially discontinuous nature of the population statistics, urban land cover information at a 30 m × 30 m resolution was used along with population data. A population density was calculated by dividing the population of a city by the number of urban pixels falling within the city boundary. Popu...

The Suitable Region and Site for 'Fuji' Apple Under the Projected Climate in South Korea

Information on the expected geographical shift of suitable zones for growing crops under future climate is a starting point of adaptation planning in agriculture and is attracting much concern from policy makers as well as researchers. Few practical schemes have been developed, however, because of the difficulty in implementing the site-selection concept at an analytical level. In this study, we suggest site-selection criteria for quality Fuji apple production and integrate geospatial data and information available in public domains (e.g., digital elevation model, digital soil maps, digital climate maps, and predictive models for agroclimate and fruit quality) to implement this concept on a GIS platform. Primary criterion for selecting sites suitable for Fuji apple production includes land cover, topography, and soil texture. When the primary criterion is satisfied, climatic conditions such as the length of frost free season, freezing risk during the overwintering period, and the late frost risk in spring are tested as the secondary criterion. Finally, the third criterion checks for fruit quality such as color and shape. Land attributes related to these factors in each criterion were implemented in ArcGIS environment as relevant raster layers for spatial analysis, and retrieval procedures were automated by writing programs compatible with ArcGIS. This scheme was applied to the A1B projected climates for South Korea in the future normal years (2011-2040, 2041-2070, and 2071-2100) as well as the current climate condition observed in 1971-2000 for selecting the sites suitable for quality Fuji apple production in each period. Results showed that this scheme can figure out the geographical shift of suitable zones at landscape scales as well as the latitudinal shift of northern limit for cultivation at national or regional scales.

Using Thermal Time to Simulate Dormancy Depth and Bud-Burst of Vineyards in Korea for the Twentieth Century

Abstract A winter-season warming trend has been observed in eastern Asian countries during the last century. Significant effects on dormancy and the subsequent bud-burst of deciduous fruit trees are expected. However, phenological observations are scant in comparison with long-time climate records in the region. Chill-day accumulation, estimated from daily maximum and minimum temperature, is a reasonable proxy for dormancy depth of temperate-zone fruit trees. A selected chill-day model was parameterized for the Campbell Early grapevine, which is the major cultivar (grown virtually everywhere) in South Korea. To derive model parameters (threshold temperature for chilling and the chilling requirement for breaking dormancy), a controlled-environment experiment using field-sampled twigs of Campbell Early was conducted. The chill-day model to estimate bud-burst dates was adjusted by derived parameters and was applied using 1994–2004 daily temperature data obtained from the automated weather station in the vine...

Quantification of Temperature Effects on Flowering Date Determination in Niitaka Pear

Most deciduous trees in temperate zone are dormant during the winter to overcome cold and dry environment. Dormancy of deciduous fruit trees is usually separated into a period of rest by physiological conditions and a period of quiescence by unfavorable environmental conditions. Inconsistent and fewer budburst in pear orchards has been reported recently in South Korea and Japan and the insufficient chilling due to warmer winters is suspected to play a role. An accurate prediction of the flowering time under the climate change scenarios may be critical to the planning of adaptation strategy for the pear industry in the future. However, existing methods for the prediction of budburst depend on the spring temperature, neglecting potential effects of warmer winters on the rest release and subsequent budburst. We adapted a dormancy clock model which uses daily temperature data to calculate the thermal time for simulating winter phenology of deciduous trees and tested the feasibility of this model in predicting budburst and flowering of Niitaka pear, one of the favorite cultivars in Korea. In order to derive the model parameter values suitable for Niitaka, the mean time for the rest release was estimated by observing budburst of field collected twigs in a controlled environment. The thermal time (in chill-days) was calculated and accumulated by a predefined temperature range from fall harvest until the chilling requirement (maximum accumulated chill-days in a negative number) is met. The chilling requirement is then offset by anti-chill days (in positive numbers) until the accumulated chill-days become null, which is assumed to be the budburst date. Calculations were repeated with arbitrary threshold temperatures from to (at an interval of 0.1), and a set of threshold temperature and chilling requirement was selected when the estimated budburst date coincides with the field observation. A heating requirement (in accumulation of anti-chill days since budburst) for flowering was also determined from an experiment based on historical observations. The dormancy clock model optimized with the selected parameter values was used to predict flowering of Niitaka pear grown in Suwon for the recent 9 years. The predicted dates for full bloom were within the range of the observed dates with 1.9 days of root mean square error.

Geospatial Assessment of Frost and Freeze Risk in `Changhowon Hwangdo` Peach (Prunus persica) Trees as Affected by the Projected Winter Warming in South Korea: I. Determination of Freezing Temperatures

We investigated the patterns of freeze injury in dormant `Changhowon Hwangdo` peach fruit by observing the extent of browning and germination of the branches that were treated with freezing temperature sets simulating the process of natural freezing incidences in orchards. Under the treatment of freezing temperature of , the browning ratios were 15% for flower bud and less than 3% for both leaf bud and cambium. Under the treatment, the browning ratios were 40% for both flower and leaf buds and 1% for cambium. The browning ratios were 86%, 68% and 40% respectively for flower bud, leaf bud, and cambium under the treatment. All the samples showed 100% browning ratio under the treatment. The budburst ratios of leaf buds were 85%, 66%, 32%, and 0% under the -15, -20, -25 and treatments, respectively. The branches of peach fruit treated with the same freezing temperature showed different responses depending on the sampling date. In January the browning ratio was low and the budburst ratio was high whereas in February the opposite was the case, showing vulnerability of peach trees to low temperature after endo-dormancy release.

Performance of Angstrom-Prescott Coefficients under Different Time Scales in Estimating Daily Solar Radiation in South Korea

While global solar radiation is an essential input variable in crop models, the observation stations are relatively sparse compared with other meteorological elements. Instead of using measured solar radiation, the Angstrom-Prescott model estimates have been widely used. Monthly data for solar radiation and sunshine duration are a convenient basis for deriving Angstrom-Prescott coefficients (a, b), but it is uncertain whether daily solar radiation could be estimated with a sufficient accuracy by the monthly data - derived coefficients. We derived the Angstrom-Prescott coefficients from the 25 years observed global solar radiation and sunshine duration data at 18 locations across South Korea. In order to figure out any improvements in estimating daily solar radiation by replacing monthly data with daily data, the coefficients (a, b) for each month were derived separately from daily data and monthly data. Local coefficients for eight validation sites were extracted from the spatially interpolated maps of the coefficients and used to estimate daily solar radiation from September 2008 to August 2009 when, pyranometers were operated at the same sites for validation purpose. Comparison with the measured radiation showed a better performance of the daily data - derived coefficients in estimating daily global solar radiation than the monthly data - derived coefficients, showing 9.3% decrease in the root mean square error (RMSE).

A Geospatial Evaluation of Potential Sea Effects on Observed Air Temperature

This study was carried out to quantify potential effects of the surrounding ocean on the observed air temperature at coastal weather stations in the Korean Peninsula. Daily maximum and minimum temperature data for 2001-2009 were collected from 66 Korea Meteorological Administration (KMA) stations and the monthly averages were calculated for further analyses. Monthly data from 27 inland sites were used to generate a gridded temperature surface for the whole Peninsula based on an inverse distance weighting and the local temperature at the remaining 39 sites were estimated by recent techniques in geospatial climatology which are widely used in correction of small - scale climate controls like cold air drainage, urban heat island, topography as well as elevation. Deviations from the observed temperature were regarded as the `apparent` sea effect and showed a quasi-logarithmic relationship with the distance of each site from the nearest coastline. Potential effects of the sea on daily temperature might exceed cooling in summer and warming in winter according to this relationship. We classified 25 sites within the 10 km distance from the nearest coastline into `coastal sites` and the remaining 15 `fringe sites`. When the average deviations of the fringe sites ( for daily maximum and for daily minimum temperature) were used as the `noise` and subtracted from the `apparent` sea effects of the coastal sites, maximum cooling effects of the sea were identified as on the west coast and on the east and the south coast in summer months. The warming effects of the sea in winter ranged from on the west and on the south and east coasts.

Geospatial Assessment of Frost and Freeze Risk in 'Changhowon Hwangdo' Peach (Prunus persica) Trees as Affected by the Projected Winter Warming in South Korea: III. Identifying Freeze Risk Zones in the Future Using High-Definition Climate Scenarios

The geographical distribution of freeze risk determines the latitudinal and altitudinal limits and the maximum acreage suitable for fruit production. Any changes in its pattern can affect the policy for climate change adaptation in fruit industry. High-definition digital maps for such applications are not available yet due to uncertainty in the combined responses of temperature and dormancy depth under the future climate scenarios. We applied an empirical freeze risk index, which was derived from the combination of the dormancy depth and threshold temperature inducing freeze damage to dormant buds of `Changhowon Hwangdo` peach trees, to the high-definition digital climate maps prepared for the current (1971-2000), the near future (2011-2040) and the far future (2071-2100) climate scenarios. According to the geospatial analysis at a landscape scale, both the safe and risky areas will be expanded in the future and some of the major peach cultivation areas may encounter difficulty in safe overwintering due to weakening cold tolerance resulting from insufficient chilling. Our test of this method for the two counties representing the major peach cultivation areas in South Korea demonstrated that the migration of risky areas could be detected at a sub-grid scale. The method presented in this study can contribute significantly to climate change adaptation planning in agriculture as a decision aids tool.