Transcript Presentation

North-East Black Sea climate system
decadal variability
Vasiliy Melnikov, Lidija Moskalenko and Natalija Kuzevanova
P.P.Shirshov Institute of Oceanology RF Academy of Sciences, Moscow,
Russian Federation, Physical oceanography dept.
[email protected] ,
[email protected],
[email protected]
Introduction
We present an analysis of meteorological and hydrophysical variability in the vicinity of Black sea North-East
coast with the use of satellite sea level anomaly (SLA), sea surface temperature (SST) databases, in-situ
temperature measurements and meteorological stations standard data.
In addition to satellite data calibration, particular goal was to examine meteorological forcing on SLA and
SST fields in order to study ocean-atmosphere interactions through descriptive elements of coastal weather
system.
Despite the present study revealed several typical properties of the Gelendzhik coastal “weather machine”,
there are essential opportunities for further combined meteorological and hydrophysical processes
examination on the basis of satellite and in-situ measurements.
On the basis of the Gelendhzik coastal weather station(44.55_N, 38.05_E) long-term (1974-2010) observational
data, climatic variability organization from a variety of synoptic conditions is considered. The mechanism of
evolution of fields from small to large time scales is the "universal" set of wind vector variations, which due to
their crucial role for the region deserves a special name "elementary cycle" (EC). Typical changes in the EC are
characterized by a cyclic change in dominant wind from the south-east to north-east direction and vice versa. The
similarity of temporal EC variations at different time scales is regarded as a manifestation of wind variability
fractality. It is shown, that the fractality is due to recurrence of basic regional baric synoptic fields. Three long-term
EC in the period 1974-2010 constitute a decadal climatic "wave" – repeated wind vector variations, which due to
rather simple appearance can be traced easily with the use of progressive vector diagram without any filtration.
This type of long-term EC figure can be used effectively as a reference curve for the numerous climatic “events”
and processes, considered in nowdays. Meridional component of wind velocity in the climatic wave, as well as the
accompanying changes in temperature of air and water, are statistically associated with the atmospheric pressure
East Atlantic-West Russia dipole. Effects of North Atlantic Oscillation are revealed in the air zonal transport
changes.
As follows from the estimate of linear trends over the past 30 years, the background warming is 0.072C/year
for sea water and 0.051C/year for the air. Similar estimation for the 70-year time series yields 0.009C/year
and 0.011C/year, respectively. During this period, 43-year temperature cycle in 1947-1990 was followed by a
half-cycle (incomplete) in 1990-2005 with a shorter period, and the amplitude of temperature long-term variations
since 1990 is clearly increased. For the other hydrometeorological parameters, amplitude and frequency of
long-term oscillations were also changing in the time course. Thus, the duration of the low-frequency sea level
cycles in the period 1995-2010 had been increased to 7 years as compared to 3 years during 1980-1995. The
according amplitude was increased from 5 to 10 cm. The reverse pattern is visible in the long-term changes of
atmospheric pressure and precipitation: the amplitude and period of recurrence in the second half of observations
at weather station were significantly decreased. The reasons for the above changes of the oscillation modes and
their relationship with atmospheric circulation indices, has not yet been clarified.
In general, the impact of winds on regional multiscale hydrophysical processes in the North-East Black Sea is
rather complicated. However, for the above relatively simple wind cycles the dominant response signals of the
marine hydrosystem can be separated. The response to winds is due to the air temperature advection, wind
strength, direction, duration and spatial inhomogenity. Currently, it is obtained, that the "quanta" of wind cycles
produces sea-level fluctuations of different time and space scales, which adapt to the equilibrium by means of
various dynamical processes including inertial waves, shelf upwellings/downwellings, local jet streams and various
eddies.
Region
North-East Black Sea part under consideration extends in the square 43-45.5N, 36.5-39E and embraces
Cemesskaya Bay, Blue Bay and Gelendzhik Bay (Fig. 1) along the shore. The shelf in this region is
rather narrow, extending only five to seven nautical miles from the shore. To the north from the 44.7N, the shelf
becomes much broader. The continental slope is regular along the coast and very abrupt in the cross-shore
direction, the depths being increasing from 100 m to 2200 meters. Along the shore moderate mountains
(up to 600 m high) chains (with rare passages across chains) form a weak shelter against cold north air spreading.
It is this along-shore Earth surface and bottom relief regularity (symmetry), which determines to a large extent the
character of regional dynamical processes in the atmosphere and in the sea.
It is well-known, that besides the advection (horizontal and vertical), North-East Black Sea
hydrophysical parameters variability in a broad regimes and scales are governed to a large extent
by atmospheric influences, such as atmospheric pressure, wind stress, heat and moisture exchange.
There are several interesting examples of atmospheric “events” and their hydrophysical
consequences, such as wind-driven Black Sea Main Current intensification, eddies production
enhancement, Novorossiysk bora far sea traces, local off-shore jets(Colchis) and larger atmospheric
cyclonic (storms) field signatures, shelf-break upwellings, A.G.Zatsepin and M.V.Flint (2002).
Fig.1 The Black Sea North-East coast Earth surface topography 3-D view of the area under
consideration. 1-minute resolution bathymetry data from Smith, W. H. F., and D.T. Sandwell (1997).
Global system of atmospheric circulation associated with the Jets -subtropical and polar jet streams in the upper
troposphere, is transforming over the Caucasian highlands and forms a regional system. Regional climatic
features of the Black Sea are the result of geographical location,orographic irregularities and smoothing effect of
the sea water. Large seasonal variations are related to the inflows of cold air from the north, warm air from the
south, as well as to the impacts of storm cyclones coming from the Mediterranean Sea.
Fig.2 Bottom topography and orography in the vicinity of the Black and Azov Seas. From Smith, W.H.F. and
DTSandwell (1997), Global seafloor topography from satellite altimetry and ship depth soundings, Science, v.
277, 1957-1962. Scale of heights and depths, in tens of meters, the resolution of the space -1 minute.
The Data and Data Processing
For the purposes of our research, we divided the total North-East region into three parts: the nearest to the Blue
Bay part includes shelf measurement sites, which data were used for different instrumentation comparison; the
second area covers dynamically active domain over the continental slope; the third - embraces the whole region (
Fig.2). The following data were used:
1. Mooring(44.57N,37.98E) sea surface temperature,1 hour sampling,1998- 2003.
2. Coastal station (44.55N, 38.05E) meteorological parameters, including wind
speed and directions, air temperature (sampling 3 hrs.), water temperature, sea
level (sampling 6 hrs.), atmospheric pressure (daily), 1990-2009.
3. Satellite Black Sea surface temperature, nightly, of AVHRR Pathfinder SST v5
array, spatial resolution 4 km, 1985-2008.
4. AVISO altimetry data Black Sea level anomaly, daily, spatial resolution 1/8,
2000- 2008.
5. Precise bottom topography “ETOPO-1” data base, spatial resolution 1‘.
The non-stationary records were detrended and filtered to remove high-frequency variations.
Synchronized parts of time rows had been converted to a set of auto and cross spectra.
Fig.3 Measurements sites. Notations: 1)red star–Shirshov Institute pier (Blue Bay, 44.58N,
37.98E); 2)red square - Gelendzhik meteostation (44.55N, 38.05E); 3)green dots–satellite
temperature data(1985-2008), nightly SST, AVHRR, NOAA; 4)pink squares-Black Sea SLA(sea level
anomaly), AVISO products. Fuzzy blue lines-bottom topography isolines; orange lines-Earth surface
orography (without heights); red dashed lines separate three polygons under analysis.
Wind system
The basic features of the regional wind variability are governed by the relevant types of the large-scale
synoptic atmospheric processes, which depends upon the state of the global atmospheric circulation, their largescale gyres and separate smaller vorticity cells. The following classification of the 4 types of annual wind
regimes can be deduced on the basis of the multy-year meteo-station annual wind direction probability diagrams
( Fig.4). In particular, in 1990-1993 winds of North rhumb were dominated. In the course of 1994-2001, 2007-2008,
there were frequent North–East winds. In the period of 2002-2006, we can distinguished persistent East winds.
In 2004-2005 practically equally frequent East and South winds were observed. Related mean annual
temperature characteristic of the above mentioned wind type periods are as follows. North wind regime (1993)
was anomalously cold; North-East winds were accompanied by variety of temperature states: warm (1998, 1999,
2001, 2007), moderate-warm (1994-1996, 2000, 2008) and moderate-cold (1997), depending upon the
characteristics of interacted air masses; East regime can be moderate-cold (2003), moderate-warm (2006) and
warm (2002). Years of the East and South winds are predominantly moderate-warm (2004) and warm (2005).
ссз
с
ссв
сз
св
зсз
всв
з
в
15 %
0
5
10
зюз
вюв
юз
юв
ююз
ю
ююв
Fig.4 Wind direction frequency occurrence for the period 1980 - August 2010.Basic wind direction intervals:
N(C) - 337.5-0-22.5; NE(CB)- 22.5-45-67.5; E(B)- 67.5-90-112.5;SE(ЮВ)- 112.5-135-157.5; S(Ю)- 157.5180-202.5; SW(ЮЗ)- 202.5-225-247.5; W(З)- 247.5-270-292.5;NW(CЗ)-292.5-315-337.5.
distance, thousand km
200
100
1971-2011
0
-100
-200
-300
-1000
1971
1990 1980
2005
2010
1975
1985
1995
2000
North
-500
distance, thousand km
0 100
100
distance, х100 km
A
0
June
Jan.
2007
Jul
Sept.
-100
March
June
-200
-300
B
March
June
Sept.
2007 - 2009
Jan.
2010
-600
Jan.
March 2008
Jan.
2009
-500
North
-400 -300 -200 -100
distance, х100 km
Fig. 6 A- long-term wind variations; B- typical seasonal cycles(Elementary cycle- EC).
0
100
30
June,17,20085 July,28,2008
May February,10 - May,10, 2008
10
distance, х100 km
distance, х100 km
20
Feb.,10,
2008
April
0
-10
March
-20
4
3
2
1
28 July 17 June
North
-60
-50
-40 -30 -20 -10
distance, х100 km
0
-1
-2
10
10
Nov.,15, 20070 Feb.,15, 2008
1 Dec.
1 Jan.
2008
-50
1 Feb.
10
15 Nov.
2007
distance, х100 km
distance, х100 km
1 July
0
A
15 фев
North
5
-50
distance, х100 km
4
1 June
D
10 June
North
0
-100
-1
0
1
2
3
distance, х100 km
May,10,2008
June,10, 2008
15 Feb.
C
B
0
10
-5
North
10 May
0
distance, х100 km
5
Fig. 7 A- first phase of the EC(SE wind); B - second phase of the EC (the transitional period of weak winds
in different directions), C - the third phase of the EC (NE winds), and E - transition period breeze fluctuations.
A
B
C
D
E
F
Fig. 8 Typical atmospheric pressure fields as related to basic types of wind conditions: A Northern, B - North-east, C - East, D - South-east,​​ E – South-west, F - North-west.
B-High, H-Low pressure.
10
U
V
A
U,V, m/s
0.5
0
-0.5
-1
-1.5
1980
1985
1990
1995
years
2000
2005
water and air temperatures, C
1
B
8
6
4
2
0
1980
2010
1990
1995
years
2000
2005
2010
1995
years
2000
2005
2010
1
1
D
C
0.5
EAWR index
0.5
NAO index
1985
0
-0.5
-0.5
-1
1980
0
1985
1990
1995
years
2000
2005
2010
-1
1980
1985
1990
Fig. 9. Characteristics time course : A – filtered smoothed velocity components of air transport of U (+ - to
the east, the solid line), V (+ - to the north, dashed line), B - filtered winter (February) sea surface
temperature (top curve - dashed) and air temperature (lower solid curve); C – filtered NAO index;
D - filtered EAWR index .
№
Row
Correlation
coefficient
95% confidence
interval
Zero correlation
probability
(p-parameter)
Linear
regression
coefficient
1
NAO - U
0.58
0,25-0,79
2*10-3
0.69
2
3
NAO - V
NAO - Ta
-0.093
-0.15
-0.46-0,31
-0.51-0,26
0.65
0.48
-0.15
-1.41
4
5
NAO - Tw
EAWR - U
-0.28
0.23
-0.60-0,12
-0.18-0,56
0.16
0.26
-1.32
0.37
6
7
8
9
EAWR - V
EAWR - Ta
EAWR - Tw
Ta-Tw
-0.27
-0.37
-0.36
0.65
-0.60-0,13
-0.67-0,015
-0.66-0,025
0.35-0,83
0.18
0.06
0.07
-0.32
-4.34
-2.05
0.31
3*10-4
Table 1. The correlation coefficients of hydro-meteorological parameters with the indices
of atmospheric circulation NAO and EAWR.
18
water temperature
510
17
sea level, cm
temperature, С
500
16
15
14
13
1985
1990
1995
years
2000
2005
460
1980
2010
1990
years
2000
2010
3.5
3
1016
2.5
1015
rain, mm
pressure,mBars
470
air temperature
1017
1014
2
1.5
1013
1
1012
1011
480
450
12
11
1980
490
1985
1990
1995
years
2000
2005
0.5
1980
1985
1990
1995
years
2000
2005
2010
Fig.10 Long-term variations (trends) of hydrometeorological parameters on the Gelendzhik weather station
during 1980-2009. Thin solid lines – filtered values​​, the filter ½ year; solid line-filter 1 year, dotted and
dashed lines are linear trends and the approximation of a polynomial of degree 10.
17
1
water temperature
baric structure index
temperature, С
16
15
14
13
12
11
0.5
NAO
EAWR
EA
POL
0
-0.5
air temperature
1940
1950
1960
1970 1980
years
1990
2000
2010
-1
1950
1960
1970
1980
years
1990
2000
2010
Fig.11 Sea surface and surface air temperature long-term variations at the Gelendzhik weather station in the
period 1938-2009, and atmospheric indices trends in the period 1950-2009 ; NAO (North Atlantic
Oscillation), - EAWR (East Atlantic - West Russia), - POL (Polar / Eurasia Pattern), - EA (East Atlantic
Pattern).
60
50
40
30
1
2
20
3
A
0
July,2008
5
4
10
August
September
October
November
B
temperature, С
30
25
20
15
10
5
0
Jan.2007
July
Jan.2008
July
Jan.2009
July
Jan.2010
time,months
Fig.12 A time-course: sea level (H-430 cm) - 1; SST (C) - 2; wind gust speed (m/s) - 3; wind speed (m/s) 4; wind direction Azimuth (grad./100) - 5, during the development of strong upwelling on August 1, September
1 and September 28, 2008, B-average sea surface temperature at weather stations in Gelendzhik in the
period 2007 to 2010.
Fig 13 IR image of the Black Sea from NOAA satellite, June 29,1998.
Fig.14 Fragments (15 km-20 km)
of images obtained by radar
ASAR satellite Envisat, showing
the spiral small-scale eddies,
typical for warm season: a - two
cyclonic eddies with diameters of
3.75 km (A) and 3 km (B); b - a
cyclonic vortex with diameter of
3.5 km (C); в - cyclonic eddy
with a diameter of 2.5 km (D); r cyclonic eddy with diameter of
5.3 km (E).
Геленджикская
бухта
а1?
Fig.15 The velocity field in the coastal-shelf zone in the region of Gelendzhik according ADCP surveys of
27-30.09 (a) - (d). The dotted line denotes the position of the alleged sub​​-mesoscale anticyclonic eddies A1 and
A2, as well as cyclonic vortex C1.
Conclusions
1. A typical feature of the regional climate system are the cyclic transitions from the north-east wind to southeast and back again.
2. Several long-term Elementary cycles(EC) constitute climatic "wave" of annual variations in wind direction
from the direction of the north-west (average wind - SE) to the direction to the southwest (average wind - NE).
3. Resemblance of the temporal structure of wind variations for the EC of different scales is viewed as fractal
variability of wind associated with the recurrence of the NE and SE types of synoptic atmospheric processes,
prevailing in the region of the North Caucasian coast.
4. Meridional component of wind velocity in the climatic wave, as well as the accompanying variations in air and
water temperatures associated with the atmospheric baric dipole EAWR. NAO influence is manifested in
changes in the zonal transport of air.
5. Bringing more air from the south to the north corresponds to the negative EAWR. phase. Accordingly,
interannual air and water temperatures are increasing with an increase in the positive (from south to north)
meridional air transport
6. Several different long-term cycles superimposed on parameters trends have been mentioned.
7. Typical winds give rise to a number of sea dynamic processes.of wide-range spatial and time scales.
References
1. Zatsepin, A.G. and Flint, M.V. (Editors), (2002), “Multidisciplinary Investigations
of the North-East Part of the Black Sea”, ”Nauka”, Moscow, 475 p.
2. Smith, W. H. F., and D.T. Sandwell (1997), “Global seafloor topography from
satellite altimetry and ship depth soundings”, Science, v. 277, 1957-1962.
Thank you for attention