JCDP

NEWS

2024.1.22

New Book on Japan’s Climate Published
2023.10.7

Invitation to International Symposium Commemorating the 200th Anniversary of Siebold’s Arrival in Japan (Online Zoom)
2021.11.19

Climate Atlas (Japan) was renewed
2021.11.14

JCDP is in the process of updating the website
2021.3.14

PAGES- CRIAS 3rd workshop: State of the Art of Historical Climatology in International Perspective will be held online Zoom on March 19-20, 2021
2021.1.18

Reconstructed Typhoon Landfall Data is released
2018.8.7

ACRE (Atmospheric Circulation Reconstructions over the Earth) Meeting in Tokyo will be held in November, 2018
2018.2.11

Diaries of the Nagasaki-Dejima Chief 1700-1860, 1817-1823 are uploaded
2018.1.29

JCDP(Japan-Asia Climate Data Program) website was fully renewed !

Welcome to JCDP !

What does Climate Data mean ? Climate Data here include not only meteorological data, but also various kinds of climate information such as documentary records describing daily weather and seasonal phenomena during the historical period. JCDP will provide information on all sorts of climate data in Japan and Asia from the past to the present.

In Japan, official meteorological observations started at Hakodate Local Meteorological Observatory in 1872 founded by the present Japan Meteorological Agency (JMA). However, our research group discovered dozens of documents which include sub-daily meteorological data observed throughout locations in Japan, such as in Nagasaki, Kobe, Osaka, Yokohama, Tokyo, Mito, Hakodate and so on during the 19^th century. Also in East Asia and Southeast Asia, a huge amount of meteorological records, which cover the 19th and 20th centuries up to World War II, have been kept safe in libraries and museums, or in some cases left to decay.

Apart from meteorological data, there are several kinds of historical documentary sources which enable reconstructions of climate variations before the 19th century in and around Japan. Historical documents including diaries of individuals, logs of clan offices, government documents and reports from temples and shrines have been preserved in local libraries and museums. These often contain daily weather descriptions such as “cold”, “fine”, “rainy” and “windy”, and mention special climate-related natural phenomena such as “lake freezing” and “flower blooming”. Information about special climate-related natural phenomena such as “lake freezing” and “flower blooming” are also contained in historical documents.

An example of daily weather records in local diaries (Hirosaki City Library)

Imaging and digitization of old paper-based instrumental meteorological records and daily weather records must be carried out before these records are lost or decay. This kind of activity is now called “DATA RESCUE”, and is taking places at many institutions all over the world. In Japan, we have also been working on “data rescue” for Southeast and East Asian instrumental meteorological records taken before the founding of official meteorological agencies.

After rescuing and digitizing the data, it is also important to share the data, therefore this “Japan-Asia Climate Data Program” (JCDP) website is aiming at distributing the data. Besides the instrumental records, data-sets of weather descriptions collected from Japanese historical documents are also included and made available to the public through this website. Past climate reconstructions based on these kind of documentary sources would be essential for not only understanding past climate variability but also projections for future climate.

Topics

Anomaly maps in “Climate Atlas”

　　　　　　　　　　　　　　　　　　　　　　　
Junpei Hirano

In climatology, we use values called “anomalies” to understand the average state of climatic elements (atmospheric pressure, temperature, precipitation, sunshine duration, and solar radiation, etc.). The “normal” is defined as the average value of climatic factors during the past 30 years. Since the average value changes due to climate change such as global warming, the normal is updated every ten years. For example, for the 10-year period from 2011 to 2020, the 1981-2010 average was used as the “normal,” but it was updated in 2021, and for the 10-year period from 2021 to 2030, the 1991-2020 average will be used as the “new normal.

In weather forecasting, the term “warmer (colder) than normal” is sometimes used, but in this case, “normal” refers to the “normal” value of temperature. In other words, the “normal value” of temperature is the standard for evaluating the warmth (coldness), etc. of each year. The difference between the temperature of each year and the normal is called the ” anomaly”. In the case of temperature, a positive anomaly indicates a warmer than normal year, while a negative anomaly indicates a colder than normal year. A map of temperature anomalies shows the distribution of areas with warmer-than-normal temperatures (positive anomaly areas) and areas with colder-than-normal temperatures (negative anomaly areas).

Similar to temperature, precipitation can also be plotted based on the “normal” value. However, in the case of precipitation, anomalies are generally expressed as the ratio of precipitation to the normal (ratio of normal to precipitation). For example, if you draw a precipitation anomaly map for a year with an El Niño or La Niña event, you can see areas with more or less rainfall than normal. Global precipitation anomaly maps for summer (June-August) and winter (December-February) of El Niño events are available on the Climate Atlas “World” page. However, as the basis for the anomalies, we have used the 43-year average for the period 1979-2021, for which precipitation data are available, instead of the 30-year “normal. Green-colored areas indicate areas of higher-than-normal rainfall, while brown-colored areas indicate areas of lower-than-normal rainfall. It can be seen that in El Niño years, there is more rainfall in the eastern tropical Pacific and less in the western tropical Pacific.

Furthermore, by comparing the precipitation anomaly map with the SST anomaly map, we can see the relationship between SST anomalies and precipitation anomalies. For example, in the “Winter DJF SST anomaly map for El Niño years”, the eastern tropical Pacific is colored red, indicating that SSTs are higher than normal. In an El Niño year, the sea surface temperature in this region is high, which activates cumulus convection and leads to heavy rainfall.

Global precipitation anomaly maps for summer (June – August) and winter (December – February) La Niña years show the opposite pattern (heavy rainfall in the eastern tropical Pacific and less rainfall in the western tropical Pacific). In La Niña years, sea surface temperatures (SSTs) drop below normal in the eastern tropical Pacific (see SST anomaly distribution in La Niña years), which suppresses cumulus convection and results in less rainfall.

The JCDP “Climate Atlas” will include various climate anomaly maps in the future. We recommend that you use the anomaly maps in the JCDP Climate Atlas when explaining “extreme weather” and its spatial distribution in high school geography and geology courses and in university liberal arts courses.