Takehiko Mikami

Pre-1872 Extension of the Japanese Instrumental Meteorological Observation Series back to 1819

Instrumental observations from Dejima (Nagasaki), Japan, taken under the responsibility of the Dutch, covering the periods 1819-28, 1845-58, and 1871-78, have been recovered. The Dejima series overlaps by six months the modern Nagasaki Observatory series, which covers 1878-present. The recovered data extend the start of the instrumental Japanese series back from 1872 to 1819, leaving major gaps during 1829-44 and 1859-71.

Enhanced atmospheric transport of soil derived organic matter in spring over the high Arctic

Arctic aerosol samples collected from Alert (82.5°N) have been studied using a capillary GC and GC/MS for long chain α,ω-dicarboxylic acids that are produced in soils by bacterial ω and ω-1 oxidations of plant-derived fatty acids. Here, we report the discovery that one month after sunrise in the Arctic, atmospheric concentrations of the soil derived, long chain dicarboxylic acids are significantly (ca. 10 times) enhanced in the high Arctic. Relative abundances of long chain diacids in aerosol total carbon contents also increased in late April to early May. In March to May during peak concentrations, the relative distribution of C20–C26 diacids in the Arctic aerosols was similar to those of Chinese loess samples, suggesting atmospheric transport of Asian dusts over distances of three to five thousand kilometers into the Arctic. This conclusion is supported by air parcel trajectory analyses which showed stronger transport from southern desert regions during peaks in long chain dicarboxylic acids in the Arctic.

Changes in the Southwest Monsoon mean daily rainfall intensity in Sri Lanka: relationship to the El Niño–Southern Oscillation

Abstract Daily rainfall data for 187 stations in Sri Lanka spanning the period 1960–1996 were analyzed to investigate the spatial and temporal characteristics of the mean rainfall intensity (MRI) through this time interval with special focus on the Southwest Monsoon (May–September). Particular emphasis was laid on temporal changes in the MRI series. The mean and standard deviation (SD) of the MRI data showed considerable spatial variation. Regression analysis expressing precipitation as a function of time at the various stations revealed distinct spatial trends; the results point to high MRI in lowland areas and low MRI in mountain areas. Principal Components Analysis of the temporal relationships among a reduced set of stations located in an equal-sized grid showed that the three dominant principal components (PCs) are characterized by the maximum and minimum mean and SD of the MRI series together with the mean number of rainy days. The first, second and third PC modes show significant patterns of the MRI data series over the northern half, southern half and southwestern coastal belt of Sri Lanka, respectively. The time series pattern of the dominant PC modes revealed distinct changes in MRI over time. A noticeable higher value in MRI was found from 1977 to 1996; this tendency is most pronounced for the first PC mode. The time series of the Southern Oscillation Index was found to be closely related to changes in the MRI patterns associated with the first PC mode. In addition, El Nino years coincide with low values of the first PC mode. Some La Nina years show a positive response for the first and third PC modes, while there is no clear response for the MRI pattern identified by the second PC.

Thermal Influence of a Large Green Space on a Hot Urban Environment.

City-scale warming is becoming a serious problem in terms of human health. Urban green spaces are expected to act as a countermeasure for urban warming, and therefore better understanding of the micro-climate benefits of urban green is needed. This study quantified the thermal influence of a large green park in Tokyo, Japan on the surrounding urban area by collecting long-term measurements. Apparent variations in the temperature difference between the park and surrounding town were found at both the diurnal and seasonal scales. Advection by regional-scale wind and turbulent mixing transfers colder air from the park to urban areas in its vicinity. The extent of the parks thermal influence on the town was greater on the downwind side of the park (450 m) than on the upwind side (65 m). The extent was also greater in an area where the terrain slopes down toward the town. Even on calm nights, the extent of the thermal influence extended by the park breeze to an average of 200 m from the park boundary. The park breeze was characterized by its divergent flow in a horizontal plane, which was found to develop well in calm conditions late at night (regional scale wind <1.5 m s and after 02:00 LST). The average magnitude of the cooling effect of the park breeze was estimated at 39 Wm. This green space tempered the hot summer nights on a city block scale. These findings can help urban planners in designing a heat-adapted city.

Representative Air Temperature of Thermally Heterogeneous Urban Areas Using the Measured Pressure Gradient

A method to measure an area-averaged ground air temperature based on the hydrostatic equation is shown. The method was devised to overcome the problem of finding the most representative surface air temperature over a wide region, a problem that has seriously hindered the description of urban heat islands. The vertical pressure gradient is used and the hydrostatic equation is applied to estimate the average air temperature between two barometers, which is here called the hydrostatic temperature. The error analysis shows that the hydrostatic temperature can be estimated with a systematic error of 1.88C and a random error of 0.78C in the case in which the two barometers have a vertical separation of 228 m. The measured hydrostatic temperature agreed with the average of the directly measured temperature within 0.78C rms. For this barometer separation, the representative area of the hydrostatic temperature was experimentally found to be a 12-km-radius circle. The size of this area decreased when the vertical separation of the barometers decreased. The hydrostatic temperature is compared with the average directly measured temperature for various areas. The maximum correlation between them occurred for a circular area with a 12-km radius centered on the pressure measurements. The size of the representative area for this method is larger than that for the direct measurement of air temperature.

Climate Variations in Tokyo Since the Edo Period

This chapter discusses climate variations in Tokyo, based on the reconstructed summer temperatures since the eighteenth century and instrumental meteorological data from the nineteenth century to the present. During the Little Ice Age, especially in the eighteenth century, remarkable cool episodes occurred in the 1730s, the 1780s, and the 1830s. These cool conditions could be a significant reason for the severe famines that occurred during the Edo period. Around the 1840s and 1850s, near the end of the Edo period, it was rather warm, which could correspond to the end of the Little Ice Age in Japan. Although there was a low-temperature period in the 1900s, a long-term warming trend could be seen, especially in winter temperatures and daily minimum temperatures, throughout the twentieth century. While annual precipitation has been increasing during the last 30 years, relative humidity has been decreasing since the late nineteenth century. This could be the result of saturated vapor pressure rise due to warming and a loss of water bodies due to urbanization. During the last century, both warmer and wetter conditions in summer and autumn, and drier conditions in winter and spring, were documented by analyzing hythergraphs.

The 1780s: Global Climate Anomalies, Floods, Droughts, and Famines

This handbook offers the first comprehensive, state-of-the-field guide to past weather and climate and their role in human societies. Bringing together dozens of international specialists from the sciences and humanities, this volume describes the methods, sources, and major findings of historical climate reconstruction and impact research. Its chapters take the reader through each key source of past climate and weather information and each technique of analysis; through each historical period and region of the world; through the major topics of climate and history and core case studies; and finally through the history of climate ideas and science. Using clear, non-technical language, The Palgrave Handbook of Climate History serves as a textbook for students, a reference guide for specialists and an introduction to climate history for scholars and interested readers.