#include <IE.au3>

$Url = 'https://rda.ucar.edu/'
$Url2 = 'https://rda.ucar.edu/datasets/ds083.2/index.html#sfol-wl-/data/ds083.2?g=22017'
;$Url2 = "https://rda.ucar.edu/data/ds083.2/grib2/2017/2017.07/fnl_20170724_06_00.grib2" direct download link once you are logged on.
$User = 'xxxxxxxxxx'
$Pwd = 'xxxxxxx'

$test = _IEAutoLogin($Url, $User, $Pwd)

Func _IEAutoLogin($sUrl, $sUsername, $sPwd)
 ;funkey 09.09.09
 $oIE = _IECreate($sUrl)
 _IEErrorNotify(False)
 _IEErrorHandlerRegister()
 $oForms = _IEFormGetCollection($oIE)
 If @error Then
  Return SetError(1, _IEErrorHandlerDeRegister(), $oIE) ;'no forms --> no login'
 Else
  $Index = 0
  For $oForm In $oForms
   $oFormElements = _IEFormElementGetCollection($oForm)
   If IsObj($oFormElements) Then
    $IndexElement = 0
    For $oElement In $oFormElements
     If $oElement.Type = 'password' Then
      $oPwd = _IEFormElementGetObjByName($oForm, $oElement.Name)
      _IEFormElementSetValue($oPwd, $sPwd)
      For $i = $IndexElement - 1 To 0 Step -1
       $oUser = _IEFormElementGetCollection($oForm, $i)
       If $oUser.Type = 'text' Then
        _IEFormElementSetValue($oUser, $sUsername)
        ExitLoop
       EndIf
      Next
      If $oForm.action <> "0" And Not StringInStr($oForm.action, '.php') Then  ;submit
       _IEFormSubmit($oForm, 0)
       _IELoadWait($oIE)
      Else  ;click
       For $i = $IndexElement + 1 To $IndexElement + 10 ;check the next 10 elements
        $oButton = _IEFormElementGetCollection($oForm, $i)
        If $oButton.Type = 'submit' Then
         _IEAction($oButton, "click")
         ExitLoop
        EndIf
       Next
      EndIf
      Return SetExtended(_IEErrorHandlerDeRegister(), $oIE)
     EndIf
     $IndexElement += 1
    Next
   EndIf
   $Index += 1
  Next
 EndIf
 Return SetError(2, _IEErrorHandlerDeRegister(), $oIE) ;no password-field found

EndFunc   ;==>_IEAutoLogin
;=============================================go to the download links==============
Sleep(3000)
Opt("WinTitleMatchMode", 2)
$a = " - Internet Explorer"
Do
    Sleep(5)
Until WinExists($a)
$b = WinGetHandle($a)
WinActivate($B)
$c = _IEAttach ($b, "HWND")
_IENavigate ($c, $Url2) ; take me to the download links


;================================================================================================


;~ #include <InetConstants.au3>
;~ #include <MsgBoxConstants.au3>
;~ #include <WinAPIFiles.au3>

;~ ; Download a file in the background.
;~ ; Wait for the download to complete.

;~ Example()

;~ Func Example()
;~     ; Save the downloaded file to the temporary folder.
;~     ;Local $sFilePath = _WinAPI_GetTempFileName(@TempDir)
;~ 	Local $sFilePath = "D:\MalutaDownloads\"

;~     ; Download the file by waiting for it to complete. The option of 'get the file from the local cache' has been selected.
;~     Local $iBytesSize = InetGet("https://rda.ucar.edu/data/ds083.2/grib2/2017/2017.07/fnl_20170724_06_00.grib2", $sFilePath & "fnl_20170724_06_00.grib2", $INET_DOWNLOADWAIT);, $INET_FORCERELOAD)

;~     ; Retrieve the filesize.
;~     Local $iFileSize = FileGetSize($sFilePath)

;~     ; Display details about the total number of bytes read and the filesize.
;~     MsgBox($MB_SYSTEMMODAL, "", "The total download size: " & $iBytesSize & @CRLF & _
;~             "The total filesize: " & $iFileSize)

;~     ; Delete the file.
;~     ;FileDelete($sFilePath)
;~ EndFunc   ;==>Example