Comparing the Köppen-Geiger, Feddema, and UNEP Climate Classifications: An Application to Iran

doi:10.21203/rs.3.rs-508056/v1

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Comparing the Köppen-Geiger, Feddema, and UNEP Climate Classifications: An Application to Iran

https://doi.org/10.21203/rs.3.rs-508056/v1

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This study introduces the climates of Iran defined by Köppen-Geiger, Feddema’s, and UNPEP classifications that applied to a high-resolution ground-based gridded data set relative to the 1985–2017 period. Ten Köppen-Geiger climate types were found for Iran, from which Bwh, Bsk, Csa, Bsh, and Bwk cumulatively account for more than 98% of the territory. Likewise, from 36 possible Feddema’s climate types, Iran possesses fifteen climate types from which the Dry Cool, Semiarid Torrid, Semiarid Hot, Semiarid Warm, Dry warm, Semiarid Cool, and Moist Cool climates collectively occupied approximately 93% of the country. Similarly, arid, semi-arid, humid, and sub-humid UNEP climate types characterized more than 98% of Iran. A few other vertically stratified climates appeared at the highlands of Iran just because of changes in elevation and slope aspects of the mountains. The combined effect of topography and vicinity to sea also creates very distinct climate types in northern Iran. The climate maps of the three used methods reflect the joint effects of topography, latitudinal variation, and land/sea surface contrast on the climate of Iran. A pairwise comparison made between the three classifications showed a satisfactory agreement between the three schemes in representing the main climate types of Iran.

Climatology

Climate Analysis and Modeling

Köppen-Geiger

Feddema

UNEP

Thornthwaite

climate classification

Iran

Table 1

The Köppen-Geiger climate types and the criteria used to define them (after Kottek et al., 2006).

Type	Description	Criterion
A	Equatorial climates	Tmin ≥ +18 ◦C
Af	Equatorial rainforest, fully humid	Pmin ≥ 60 mm
Am	Equatorial monsoon	Pann ≥ 25(100−Pmin)
As	Equatorial savannah with dry summer	Pmin < 60 mm in summer
Aw	Equatorial savannah with dry winter	Pmin < 60 mm in winter
B	Arid climates	Pann < 10 Pth
BS	Steppe climate	Pann > 5 Pth
BW	Desert climate	Pann ≤ 5 Pth
C	Warm temperate climates	−3 ◦C < Tmin < +18 ◦C
Cs	Warm temperate climate with dry summer	Psmin < Pwmin, Pwmax > 3 Psmin and Psmin < 40 mm
Cw	Warm temperate climate with dry winter	Pwmin < Psmin and Psmax > 10 Pwmin
Cf	Warm temperate climate, fully humid	neither Cs nor Cw
D	Snow climates	Tmin ≤ −3 ◦C
Ds	Snow climate with dry summer	Psmin < Pwmin, Pwmax > 3 Psmin and Psmin < 40 mm
Dw	Snow climate with dry winter	Pwmin < Psmin and Psmax > 10 Pwmin
Df	Snow climate, fully humid	neither Ds nor Dw
E	Polar climates	Tmax < +10 ◦C
ET	Tundra climate	0 ◦C ≤ Tmax < +10 ◦C
EF	Frost climate	Tmax < 0 ◦C

Table 2

The criteria used to calculate the third letter of the Köppen-Geiger climate types (after Kottek et al., 2006).

Type	Description	Criterion
h	Hot steppe / desert	Tann ≥ +18 ◦C
k	Cold steppe /desert	Tann < +18 ◦C
a	Hot summer	Tmax ≥ +22 ◦C
b	Warm summer	not (a) and at least 4 Tmon ≥ +10 ◦C
c	Cool summer and cold winter	not (b) and Tmin > −38 ◦C
d	extremely continental	like (c) but Tmin ≤ −38 ◦C

Table 3

Definition of Feddema’s (2005) thermal and moisture types through categorizations of annual PET and I_mvalues.

Thermal type categorizations		Moisture type categorizations
Thermal type	PET (mm year⁻¹)	Moisture type	Moisture index, I_m
Torrid	>1500	Saturated	0.66-1.00
Hot	1200–1500	Wet	0.00–0.33
Warm	900–1200	Moist	900–1200
Cool	600–900	Dry	-0.33–0.00
Cold	300–600	Semi-arid	-0.66– -0.33
Frost	0-300	Arid	-1.00- -0.66

Table 4

The magnitude of climate seasonality in Feddema’s climate classification

The magnitude of climate seasonality	The annual range of I_m (I_m max −I_m min)
Low	0.0-0.5
Medium	0.5–1.0
High	1.0–1.5
Extreme	1.5-2.0

Table 5

Criteria used for identifying the causes of seasonality.

Climate variable	(P_max −P_min)/ (PET_max −PET_min)
Temperature	<0.5
Temperature and precipitation	0.5–2.0
precipitation	>2.0

Table 6

Climate types and their respective precipitation to ETo ratios adopted from Spinoni et al. (2015).

Climate type	Ratio P/PET (AI)
Desert	AI≤ 0.03
Hyper-arid	0.03 <AI≤ 0.05
Arid	0.05 <AI≤ 0.2
Semi-arid	0.2 <AI ≤0.5
Dry	0.5 <AI≤ 0.65
Sub-humid	0.65 <AI≤ 0.75
Humid	AI >0.75

Table 7

The occupied area and the associated percentage of climate types of Iran as determined with the Köppen-Geiger climate classification.

Climate type	Occupied area (%)	Occupied area (km²)
BWh	35.98	593015.26
BWk	5.94	97953.41
BSh	15.70	258782.33
BSk	23.69	390489.96
Cfa	0.20	3309.24
Cfb	0.04	661.85
Csa	17.03	280623.29
Csb	0.56	9265.86
Dsa	0.68	11251.41
Dsb	0.16	2647.39
Total area	100.00	1648000.00

Table 8

The occupied area and the associated percentage of climate types of Iran as determined with Feddema’s classification method.

Climate type	Occupied area (%)	Occupied area (km²)
Arid Torrid	2.29	37679.90
Arid Hot	0.04	661.05
Arid Warm	0.04	661.05
Semiarid Torrid	17.13	282268.75
Semiarid Hot	15.72	259131.97
Semiarid Warm	15.00	247233.05
Semiarid Cool	4.41	72715.60
Dry Torrid	2.13	35035.70
Dry Hot	1.93	31730.45
Dry Warm	9.95	163940.63
Dry Cool	26.80	441582.03
Dry Cold	0.32	5288.41
Moist Warm	0.12	1983.15
Moist Cool	3.69	60816.69
Moist Cold	0.44	7271.56
Total area	100.00	1648000.00

Table 9

The occupied area and the associated percentage of climate types of Iran as determined with the UNEP classification method.

Climate type	Occupied area (%)	Occupied area (km²)
Desert	0.00	0.00
Hyper-arid	0.32	5294.78
Arid	52.85	870991.16
Semi-arid	34.26	564555.82
Dry	6.95	114499.60
Sub-humid	1.65	27135.74
Humid	3.98	65522.89
Total area	100.00	1648000.00

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Editorial decision: Major Revisions Needed
18 Sep, 2021
Reviews received at journal
13 Jul, 2021
Reviewers invited by journal
13 Jul, 2021
Editor assigned by journal
10 May, 2021
First submitted to journal
07 May, 2021

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Comparing the Köppen-Geiger, Feddema, and UNEP Climate Classifications: An Application to Iran

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