1Instituto Pirenaico de Ecología, Consejo Superior de Investigaciones Científicas (IPE–CSIC), Zaragoza, Spain, 2Environmental Physics Laboratory, Universidade de Vigo,
Ourense, Spain, 3University of Gothenburg, GothenburgSweden
Sergio M. Vicente-Serrano1, Raquel Nieto2, Luis Gimeno2, Cesar Azorin-Molina3
Global changes in relative humidity: connection
with climate trends, humidity sources and
moisture transport processes.
STRONG IMPORTANCE IN SEVERAL ATMOSPHERIC PROCESSES
Vicente-Serrano, S.M. et al. (2014): Water Resources Research, 50, 8458
Simmons, A.J. et al (2010). J Geophys Res Atmos 115:D01110
Willett, K. M., et al. (2014): Clim. Past, 10, 1983
Dai, A. (2006): J. Climate, 19: 3589.
Sherwood and Fu (2014): Science, 343, 737.
Fu, Q., and S. Feng (2014), J. Geophys. Res. Atmos., 119, 7863–7875
Byrne, M., and P. O'Gorman, 2016: J.Climate. doi:10.1175/JCLI-D-16-0351
LAND-OCEAN DIFFERENCES
Van der Ent et al. (2010): Water Resources Research. Vol 46, W09525
Brubaker et al. (1993): Journal of Climate. 6: 1078
Bosilovich et al. (2005): Journal of Climate. 18: 1591
RECYCLING PROCESSES
OBJECTIVES
• TO DETERMINE SPATIAL AND SEASONAL PATTERNS OF RELATIVE HUMIDITY TRENDS
• TO IDENTIFY POSSIBLE DRIVERS OF RELATIVE HUMIDITY TRENDS:
CLIMATE TRENDS
CHANGES IN EVAPORATION IN OCEANIC HUMIDITY SOURCES
CHANGES IN EVAPOTRANSPIRATION IN CONTINENTAL HUMIDITY SOURCES
Station data: Relativehumidity(3462 stations)
0.5º Gridded Relativehumidity
RELATIVE HUMIDITY TRENDS (1979-2014)
Boreal cold season
-15 -10 -5 0 5 10 15
Rela
tive f
requency
0
2
4
6
8
10
12
14
16
18
0
10
20
30
40
50
Boreal warm season
-15 -10 -5 0 5 10 15
Rela
tive f
requency
0
2
4
6
8
10
12
14
16
0
10
20
30
40
50
Annual
-15 -10 -5 0 5 10 15
Rela
tive f
requency
0
2
4
6
8
10
12
14
16
18
20
0
10
20
30
40
50
HadISDH
Boreal cold season
-15 -10 -5 0 5 10 15
Rela
tive f
requency
0
2
4
6
8
10
12
14
0
10
20
30
40
50
Boreal warm season
-15 -10 -5 0 5 10 15
Rela
tive f
requency
0
2
4
6
8
10
12
0
10
20
30
40
50
Annual
-15 -10 -5 0 5 10 15R
ela
tive f
requency
0
2
4
6
8
10
12
14
16
0
10
20
30
40
50
ERA-Interim
Chi square Sig. C. Contingency
Boreal cold season 915.96 0.000 0.485
Boreal warm season 786.356 0.000 0.46
Annual 1080.115 0.000 0.516
0.5º Land Evapotranspiration
0.5º Ocean Evaporation
0.5º Precipitation and temperature
5º SST
LA PLATA
LA PLATA
LA PLATA: OBSERVED SERIES
LA PLATA: DETRENDED SERIES
WEST SAHEL
WEST SAHEL
WEST SAHEL: OBSERVED SERIES
WEST SAHEL: DETRENDED SERIES
INDIA
INDIA
INDIA: OBSERVED SERIES
INDIA: DETRENDED SERIES
Precipitation
Change in precipitation (%)
-30 -20 -10 0 10 20 30
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.18
p > 0.05
ratio Air Temp./SST
Change in ratio Air Temp./SST
-0.03 0.00 0.03 0.06 0.09 0.12 0.15
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.04
p > 0.05
Ocean Evaporation
Change in Ocean Evaporation (%)
-5 0 5 10 15 20 25
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.13
p > 0.05
Land Evaporation
Change in Land Evaporation (%)
-15 -10 -5 0 5 10 15 20 25
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.47
p < 0.05
Ratio Ocean/Land evaporation(Flexpart)
Change in Ratio Ocean/Land Evaporation (%)
-30 -20 -10 0 10 20
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.03
p > 0.05
Ratio Ocean/Land evaporation(Oaflux/Gleam)
Change in Ratio Ocean/Land Evaporation (%)
-20 -15 -10 -5 0 5 10 15 20C
han
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.46
p < 0.05
A GLOBAL SUMMARY: WARM SEASON
Precipitation
Change in precipitation (%)
-40 -30 -20 -10 0 10 20 30 40
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.47
p < 0.05
ratio Air Temp./SST
Change in ratio Air Temp./SST
0.00 0.03 0.06 0.09 0.12 0.15 0.18 0.21
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.46
p < 0.05
Ocean Evaporation
Change in Ocean Evaporation (%)
0 2 4 6 8 10 12 14 16
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.21
p > 0.05
Land Evaporation
Change in Land Evaporation (%)
-20 0 20 40 60 80
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
8
Pearson's r = 0.62
p < 0.05
Ratio Ocean/Land evaporation(Flexpart)
Change in Ratio Ocean/Land Evaporation (%)
-25 -20 -15 -10 -5 0 5 10 15
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.59
p < 0.05
Ratio Ocean/Land evaporation(Oaflux/Gleam)
Change in Ratio Ocean/Land Evaporation (%)
-40 -30 -20 -10 0 10 20 30C
han
ge i
n R
ela
tive H
um
idit
y-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.66
p < 0.05
A GLOBAL SUMMARY: COLD SEASON
Precipitation
Change in precipitation (%)
-30 -20 -10 0 10 20 30
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.31
p > 0.05
ratio Air Temp./SST
Change in ratio Air Temp./SST
0.00 0.03 0.06 0.09 0.12 0.15 0.18C
han
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.34
p > 0.05
Ocean Evaporation
Change in Ocean Evaporation (%)
0 5 10 15 20 25
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.08
p > 0.05
Land Evaporation
Change in Land Evaporation (%)
-15 -10 -5 0 5 10 15 20 25
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = 0.64
p < 0.05
Ratio Ocean/Land evaporation(Flexpart)
Change in Ratio Ocean/Land Evaporation (%)
-20 -15 -10 -5 0 5 10
Ch
an
ge i
n R
ela
tive H
um
idit
y
-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.4
p > 0.05
Ratio Ocean/Land evaporation(Oaflux/Gleam)
Change in Ratio Ocean/Land Evaporation (%)
-20 -15 -10 -5 0 5 10 15 20
Ch
an
ge i
n R
ela
tive H
um
idit
y-12
-10
-8
-6
-4
-2
0
2
4
6
Pearson's r = -0.55
p < 0.05
A GLOBAL SUMMARY: ANNUAL
Mean = 45 mm/36 years
Mean = 12.4 mm/35 years
Of this precipitation, approximately two thirds is recycled over the continents.
Gimeno et al. (2013): Reviews of Geophysics, 50.
Most of the water that evaporates from the oceans (90%) is precipitated back into them. Only 10% falls as precipitation over the continents.
CORRELATION BETWEEN ANNUAL RH AND LAND EVAPORATION
Evaporation
Negative (p < 0.05)
Negative (p > 0.05)
Positive (p > 0.05)
Positive (p < 0.05)
Magnitude of change in Land Evaporation
Magnitude of change in Relative Humidity
CONCLUSIONS
• HIGH SPATIAL VARIABILITY IN RELATIVE HUMIDITY TRENDS BETWEEN1979 AND 2014
• GOOD AGREEMENT BETWEEN OBSERVATIONS AND ERA-INTERIM DATA
• HIGH SPATIAL VARIABILITY IN THE INFLUENCE OF PRECIPITATION, LANDEVAPOTRANSPIRATION AND OCEAN EVAPORATION ON RELATIVEHUMIDITY TRENDS
• LAND EVAPOTRANSPIRATION VARIABILITY SEEMS TO BE THE MAINDRIVERS OF RELATIVE HUMIDITY TRENDS AT THE GLOBAL SCALEALTHOUGH THERE ARE STRONG SPATIAL DIFFERENCES AND IN SOMEAREAS OF THE WORLD THE INFLUENCE IS NOT CLEAR.