(Upload on February 19 2024) [ 日本語 | English ]

Climate (気候)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily



The patterns of variations of meteorological variables, such as temperature, humidity, atmospheric pressure, wind, precipitation in a given region (area) over long periods → weather (= short term)

klima (Gr.) = inclination

Climatic factor (気候因子), y
y = f(s, t, a, m, p)

s: solar radiation 日射
t: temperature 温度
a: air pressure 気圧
m: air mass 気団
p: precipitation 降水量

[electromagnetic spectrum, temperature, cloud, acid rain ]
[Hokkaido, global warming] [meteorology]

climate factors

Temperature (温度), T

Seasonal change
ΔTt = advection (移流量) - sink + source

= vertical and horiozontal advection - terrestrial radiation + solar radiation

latitudinal and daily fluctuations, in the same way

Annual temperature
annual mean temerature (T) and its related variables

monthly mean maximum temperature (月平均最高気温), Tmax
monthly mean minimum temperature (月平均最低気温), Tmin
temperature difference (温度格差), DT = Tmax - Tmin
accumulated temperature (積算温度): the sum of monthly mean temperature in a year

Warmth index (温量指数)
WI = Σ12i=1 (ti > 5), ti = mean monthly temperature > +5°C

WI is roughly consistent with the distribution of ecosystems in Japan

[cherry blossom front (桜前線)]

Climate classification (気候区分)

Temperature, T

(Kawakita & Kira 1945)

Aridity-humidity index (乾湿度指数, K)
= P/(WI + 20) (W < 100)
= P/(WI + 140) (W > 100)

WI: warmth index

< 3.0__3-5____5-7_____7-10__> 10
Desert Steppe Savanna Forest Rain forest

(Thornthwaite 1948)

Thornthwaite climate classification
Def. potential evapotranspiration (最大可能蒸発散量), E or PET:

combined loss of water through transpiration (mostly from plants) and evaporation (mostly from soils)

Def. TE percent (temperature-evaporation percent) = (T - 32)/4

mean annual temperature, T (Fahrenheit, °F): adjusted 0 °C by -32 (un-frozen temperature)

Def. TE index = Σn=112(10 × TE percent)

(Hamät-ahti et al. 1974)

Mean annual biotemperature, MABT
= Σi=112Pi/12 (case Pi > 0)

→ matched well with Japanese vegetation classification
↔ WI is used for investigating maritime and/or continental patterns of precipitation

  • Arctic (A): MABT < 3.0
  • Hemiarctic (HA), Noshery boreal (NB), Middle boreal (MB), Southern boreal (SB), Hemiboreal (HB): 3.0-7.5 (northern zone, cold zone)
  • Temperate (T), Hemitemperate (HT): 7.5-12.0
  • Meridional (M): 12.0-18.0
  • Subtropical (STR): 18.0-25.0
  • Tropical (TR): > 25.0

Precipitation, P


Pecipitation effectiveness index (降水効果指数, Ep)
Ep = Σi=1120.17{Pi/(ti + 12.1)} = 11.5P(T – 10)10/9

< 128__127-64__63-32__31-16__< 16
_______Forest_________Steppe Desert

T-P relationships

A climatic graph showing relationships between temperature and humidity or temperature and precipitation
hythergraph T: temperature
P: precipitation

Walter's climate diagram
(max) mean daily max. temperature of the warmest month
(min) mean daily min. temperature of the coldest month

Macroclimate classification (大気候区分)

Köppen climate classification (ケッペンの気候区分)

= Köppen-Geiger climate classification system
Many reworks after 1884
A: Tropical/megathermal climates
B: Dry (arid and semiarid) climates
C: Temperate/mesothermal climates
D: Continental/microthermal climates
E: Polar and alpine climates

Climate in Japan (日本の気候)

Monsoon zone

Climatic features = four seasons
Temperature ⇒ Keep high biodiversity
The wide range of yearly "temperatures"

Ex. Sakura front (cherry blossom front)

Precipitation ⇒ Climax is forests in most regions, because of plenty water
The large amount of "rainfall"

Bai-u or Tsuyu (summer rainy season)

From the southern part to northward

Typhoon season
Aki-same (fall rainy season)

(Except Hokkaido)

Snow [western and northern Japan, including Hokkaido]
Climate classification
Hokkaido: a humid continental climate with long, cold winter and warm to cool summer,
Japan Sea: northwest winter winds bring heavy snowfall. The region is cooler and little less rainy in the summer than the Pacific area, although it sometimes experiences extremely hot temperatures due to the foehn wind
Pacific Ocean: a humid temperate climate that experiences milder winter with occasional snowfall and hot, humid summer because of the southeast seasonal wind. hevy rain in the south, and in the north in the summer days
Inland(Central Highlands): a typical inland humid continental climate, with large temperature differences between summer and winter, and between day and night; precipitation is light, although winter is usually snowy.
Seto Inland Sea: the mountains of the Chugoku and Shikoku regions shelter the Seto Inland Sea from seasonal winds, bringing mild weather year-round and having many sunny days.
Nansei Islands (Southwest Islands): with hot summer and warm winter. It has heavy rain year-round, particularly in rainy season and typhoon season (≈ sub-tropical)

Climate change (気候変動)

Acid rain (酸性雨)

A rain (including fog, snow and other precipitation, s.l.) that is unusually acidic, i.e., pH < 5.6 (or 5.7)
Most acid rain is now derived from human activities, in particular, consuming fossil fuels, such as coal and oil

SO3 + H2O → H2SO4

NOX (nitrogen oxides)
= thermal NOX + fuel NOX

NO2 + OH+ → HNO3

SOX (sulfur oxides)

Worldwide background of SO2 and sulphate aerosols

----------------------------------------------------------------------------------------------- acid rain
Fig. 1. Schematic representation of the main components of the atmospheric sulfur budget from synthetic crude oil plants in a northern environment (Hammer 1980)