8.16 Surface fields

8.16.1 Description

field	hdf set	unit	times
orography (surface geopotential)	oro	m2/s2	[21,21]
land/sea mask	lsm	0-100%	[21,21]
Low vegetation cover	cvl	0-1 (day aver)	[21,21]
High vegetation cover	cvh	0-1 (day aver)	[21,21]
area fraction vegetation type ##	tv##	0-100%	[21,21]
Sea-ice cover	ci	0-1 (day aver)	[21,21]
Surface roughness Ganzeveld/Olsson	z0_ols	m (day aver)	[21,21]
Surface roughness ECMWF	z0_ecm	m (day aver)	[21,21]
Surface roughness merged	z0_mer	m (day aver)	[21,21]
Log. surface roughn. for heat	lsrh	-	00, 03, .., 21
volumentric soil water layer 1	swvl1	m3/m3 (day aver)	[21,21]
volumentric soil water layer 2	swvl2	m3/m3 (day aver)	[21,21]
volumentric soil water layer 3	swvl3	m3/m3 (day aver)	[21,21]
volumentric soil water layer 4	swvl4	m3/m3 (day aver)	[21,21]
skin reservoir content	src	m of water	00, 03, .., 21
stratiform precipation	lsp	m/s (time aver)	[21,00], .., [18,21]
convective precipation	cp	m/s (time aver)	[21,00], .., [18,21]
snowfall (convective+stratiform)	sf	m water eqv/s (t.av.)	[21,00], .., [18,21]
Wind gust at 10 metres	10fg	m/s (time aver)	[21,00], .., [18,21]
10 metre u wind	10u	m/s	00, 03, .., 21
10 metre v wind	10v	m/s	00, 03, .., 21
Boundary layer height	blh	m	00, 03, .., 21
surface sensible heat flux	sshf	W/m2 (time aver)	[21,00], .., [18,21]
surface latent heat flux	slhf	W/m2 (time aver)	[21,00], .., [18,21]
surface stress	sstr	N/m2 (time aver)	[21,00], .., [18,21]
2 metre temperature	t2m	K	00, 03, .., 21
2 metre dewpoint temperature	d2m	K	00, 03, .., 21
velocity scale	ustar	m/s	00, 03, .., 21
aerodynamic resistance	Raero	s/m	00, 03, .., 21
albedo	al	0-1 (day aver)	[21,21]
Snow depth	sd	m water eqv (day aver)	[21,21]
surface solar radiation	ssr	W/m2 (time aver)	[21,00], .., [18,21]

See section on Surface fields in the TMPP manual for how computed from raw data.

Details:

• Surface fields are defined on a global 1x1 grid.
• Surface fields are defined for 3-hour resolution times 00/03/../21, or constant in 3 hourly intervals [21,00] , [00,03] , etc., or 24 hour averages over 3 [21,21] .
• Grid cells are optionally combined by area-average.

8.16.2 Required fields

Description by Michiel van Weele and Frank Dentener in progress.

  TM3 according to Michiel                   available from ECMWF
                                                    curr   grib  MARS
  var       description                      set    file   code  abbr.  description                          unit
  -----     ----------------                 -----  ----   ----  -----  ----------------------------------   --------------
 
  ews       soil wetness                     od     SG     184   SWL3   Soil wetness level 3                 m of water
                                                                        Climatological deep soil wetness 
                                                                        (CDSW) before 19930804.
                                                                        Scaled depth surf water 7cm deep

                                             od            039   SWVL1  volumetric soil water layer 1        m3/m3
                                                           040   SWVL2  volumetric soil water layer 2        m3/m3
                                                           041   SWVL3  volumetric soil water layer 3        m3/m3
                                                           042   SWVL4  volumetric soil water layer 4        m3/m3

                                             e4            039          soil moisture level 1 (volumetric)   m 3 /m 3
                                                           040          soil moisture level 2 (volumetric)   m 3 /m 3
                                                           041          soil moisture level 3 (volumetric)   m 3 /m 3
                                                           042          soil moisture level 4 (volumetric)   m 3 /m 3
 
  esnd      snow depth                       od,e4  SG     141    SD    Snow depth                           m of water eq     

  et2m      2m temperature                   od,e4  SG     167    2T    2 metre temperature                  K

  etdew2m   2m dewpoint temp.                od,e4  SG     168    2D    2 metre dewpoint temperature         K

  esrads    net surface solar radiation      od,e4  SG     176    SSR   Surface solar radiation              W/m2 s     
                                                                        Accumulated field

  ewl       skin reservoir content           od,e4  SG     198    SRC   Skin reservoir content               m of water

  eseaice   seaice cover                     od,e4         031    CI    Sea-ice cover                        (0-1) 
  
  evgrat    vegetation ratio                 od,e4         027    CVL   low vegetation cover                 (0-1)
            (frac covered by vegetation)                   028    CVH   high vegetation cover                (0-1)

                                             od            199    VEG   Vegetation fraction                  (0-1)

  eforestm  vegetation type                  od,e4         029    TVL   low vegetation type (table index)    index
            (fraction forest/tot.veg.)                     030    TVH   high vegetation type (table index)   index

  ewsmx     field capacity                   ???           ???


See also:

  ERA40 archive plan:
    http://www.ecmwf.int/research/era/Products/Archive_Plan/Archive_plan_3.html
  
  ECMWF local table 2
    http://www.ecmwf.int/publications/manuals/libraries/tables/localTable128.html
  (according to the catalog, the available od surface parameters are:
   27/28/29/30/31/32/33/34/35/36/37/38/39/40/41/42
   /128/129/134/136/137/139/141/148/151/160/161/162/163/164/165/166/167/168/170/172/173/174/183/186/187/188/198
   /206/234/235/236/238 )

8.16.3 Surface roughness

Laurens Ganzeveld: (SR,173) is surface roughness for momentum, while required surface roughness for heat.

code	name	description	unit
173	SR	surface roughness	m
234	LSRH	Logarithm of surface roughness length for heat	-

The SR previously computed was merged between the SR from ECMWF and the SR from Ganzeveld/Olsson.

And from the book of 1001 Afternoons, our favorite fairytale Michiel and the 7 surface roughnesses:

Na enige discussie met Ge het volgende verhaaltje:

We hebben nodig: Raero en R_b

We hebben een z0m, maar die is soms erg groot want wordt bepaald uit de momentum stresses (ewss, nsss) onder invloed van o.a. orografie. Deze z0m is dus niet lokaal relevant voor depositie, maar wel voor de bepaling van uitwisseling op grotere hoogte, d.w.z. voor de berekening van Kzz. Daarom moeten we z0m als parameter handhaven.

Voor de lokale z0 baseren we ons boven zee op de ECMWF z0, aangezien hier orografie geen rol speelt (let wel op mogelijk effect van eilanden??) Boven land willen we ook een lokale z0. De beste keus daarvoor is de z0 voor heat, want gas uitwisseling en warmte uitwisseling is gerelateerd. Die z0h willen we dus ook hebben. Voor de berekening van R_b (dat doen we in de TM3 code) moeten we dan wel consistent zijn. Hier hebben we de verhouding van lokale z0m en z0h nodig. Deze stellen we daar op 1 behalve voor vegetatie waar we hem op 2 zetten. Dus ik stel voor dit in de preprocessing ook te doen met onze z0h en dit dan vervolgens onze lokale z0m te noemen.

Gegeven deze z0m's, de warmtefluxen (sshf, slhf) en het laagste windveld kunnen we vervolgens ustar en Monin-Obukhov lengte L berekenen. Hieruit berekenen we vervolgens onze Raero. En toen was het verhaaltje uit.

Michiel van Weele, November 26 2002

8.16.4 Vegetation

8.16.4.1 Vegetation ratio

ECMWF has two fields available: Low Vegetation Cover (CVL,027) and High Vegetation Cover (CVH,028) .

code	name	description	unit
027	CVL	Low vegetation cover	0-1
028	CVH	High vegetation cover	0-1

Alternative: parameter 199, but this fields is only available from the seasonal forecast.

code	name	description	unit	comments
199	VEG	vegetation fraction	0-1	-

8.16.4.2 Vegetation type

ECMWF's Type of Low Vegetation (TVL,029) and Type of High Vegetation (TVH,030) are disjunct fields with table indices. The next table is a copy taken from the IFS documentation, IV. Physical processes, Chapter 7. Land surface parametrization, 7.2 Tiles and surface fluxes, Table 7.1 .
In may 2006 it was shown that this table contains an error; the description of types 5 and 6 was swapped. The correct table is shown for example in Table 9.3 of the IFS documentation.

Vegetation types and parameter values (see text). H/L refer to the distinction between high and low vegetation.

Index	Vegetation type	H/L	rs,min (s m-1)	LAI (m2m-2)	cveg	gD (hPa-1)	ar	br
1	Crops, mixed farming	L	180	3	0.90	0	5.558	2.614
2	Short grass	L	110	2	0.85	0	10.739	2.608
3	Evergreen needleleaf trees	H	500	5	0.90	0.03	6.706	2.175
4	Deciduous needleleaf trees	H	500	5	0.90	0.03	7.066	1.953
5	Evergreen broadleaf trees Deciduous broadleaf trees	H	175	5	0.90	0.03	5.990	1.955
6	Deciduous broadleaf trees Evergreen broadleaf trees	H	240	6	0.99	0.03	7.344	1.303
7	Tall grass	L	100	2	0.70	0	8.235	1.627
8	Desert	-	250	0.5	0	0	4.372	0.978
9	Tundra	L	80	1	0.50	0	8.992	8.992
10	Irrigated crops	L	180	3	0.90	0	5.558	2.614
11	Semidesert	L	150	0.5	0.10	0	4.372	0.978
12-	Ice caps and glaciers	-	-	-	-	-	-	-
13	Bogs and marshes	L	240	4	0.60	0	7.344	1.303
14	Inland water	-	-	-	-	-	-	-
15	Ocean	-	-	-	-	-	-	-
16	Evergreen shrubs	L	225	3	0.50	0	6.326	1.567
17	Deciduous shrubs	L	225	1.5	0.50	0	6.326	1.567
18	Mixed forest/woodland	H	250	5	0.90	0.03	4.453	1.631
19	Interrupted forest	H	175	2.5	0.90	0.03	4.453	1.631
20	Water and land mixtures	L	150	4	0.60	0	-	-

For pictures of high and low vegetation and vegetation type, see: IFS documentation, IV. Physical processes, Chapter 9. Climatological data, 9.7 Vegetation parameters.